Prepared by
Box 246, North End Station
Detroit 2, Michigan
OCTOBER 1956
The 1957 Chevrolet passenger car, described in the following pages, reflects another year of intensive engineering development.
Styling changes bring new and advanced lines to the current models. New 283 cubic inch displacement V-8 engines; the Turboglide, "luxury" automatic transmission; a fuel injection system of revolutionary design; and numerous chassis improvements are illustrative of the mechanical advances available to the customer in 1957.
H. F. Barr Chief Engineer
A product of extensive engineering development, the 1957 passenger car incorporates many far-reaching new features designed to keep Chevrolet at the forefront of contemporary passenger cars in performance, styling and road ability.
All-encompassing appearance changes, larger engines, revolutionary new fuel injection, a new automatic transmission and extensive chassis revisions, combine with numerous owner-proven components to produce a vehicle outstanding in every characteristic.
The body and sheet metal changes which developers the new appearance for 1957 are many. Every detail is styled for a lower and longer silhouette, to emphasize the luxurious appearance usually associated with higher priced lines. Fenders are redesigned to accommodate the all new ventilation system, and the hood is lower and flatter. With the plenum chamber eliminated, the cowl is lower, permitting an increase in windshield glass area for all models. New rear quarter panels incorporate fins to accentuate the low, horizontal lines. Bumpers and grille are entirely new, setting the styling keynote of an integrated appearance. Bright touches of gold set off luxurious Bel Air models. Interiors display restyled instrument panels, new offset-spoke steering wheels, as well as seat design and fabrics.
A number of chassis changes augment the already outstanding qualities of ride and handling. New fourteen-inch diameter wheels are used and wider, lower pressure tires provide a softer ride. An increase in rear axle travel is provided through redesign of the rear springs and front hangers. Frame and rear axle improvements increase durability. A new chassis wiring harness, which is divided into separate units joined by bulkhead connectors, makes it unnecessary to route electrical wiring through sheet metal, resulting in greater serviceability. The ultimate in driving ease and smoothness is offered with Turboglide, the all-new automatic transmission. The transmission introduces a unique downhill retarder provision which greatly improves control on hills, while increasing brake life.
For the first time, Chevrolet offers a fuel injection system, which replaces the intake manifold and conventional carburetor, providing a more consistently accurate fuel-air mixture, with resultant increases in performance.
In addition to the six-cylinder engine and an improved 265 cubic inch displacement V-8, a larger, more powerful V-8 engine is available,. The new engine, with a 283 cubic inch displacement, is offered in four versions, ranging up to 283 horsepower when used in combination with fuel injection and high performance camshaft.
Featured on all V-8 engines, a thicker cylinder block top deck,
and improved ignition system with an advanced design distributor, and an
improved ignition system result in greater performance and durability.
Series and Models
THE 1957 LINE
See Illustrations.
Fig. 1 - Series 2400 Four-Door Sedan 6-Passenger Model 2403
Fig. 2 - Two Door Sedan 6-Passenger Model 2402
Fig. 3 - Sport Sedan 6-Passenger Model 2413
Fig. 4 - Sport Coupe 6-Passenger Model 2454
Fig. 5 - Convertible 5-Passenger Model 2434
Fig. 6 - Foor-Door Station Wagon 6-Passenger Model 2409
Fig. 7 - Two-Door Station Wagon 6-Passenger Model 2429
Fig. 8 - Four-Door Sedan 6-Passenger Model 2103
Fig. 9 - Two-Door Sedan 6-Passenger Model 2102 Club Coupe 6-Passenger Model 2124
Fig. 10 - Sport Sedan 6-Passenger Model 2113
Fig. 11 - Sport Coupe 6-Passenger Model 2154
Fig. 12 - Four-Door Station Wagon 9-Passenger Model 2119 6-Passenger Model 2109
Fig. 13 - Two-Door Station Wagon 6-Passenger Model 2129
Fig. 14 - Four-Door Sedan 6-Passenger Model 1503
Fig. 15 - Two-Door Sedan 6-Passenger Model 1502 Utility Sedan 3 Passenger Model 1512
Fig. 16 - Two-Door Station Wagon 6-Passenger Model 1529
Fig. 17 - Corvette 2-Passenger Model 2934
A greatly diversified line-up of twenty passenger cars, including the Corvette again is offered by Chevrolet for 1957. All specific models are carried over from the previous year with one exception; the nine-passenger Bel Air Station Wagon is replaced by one of six-passenger capacity. Models of each series, the 2400, the 2100 and the 1500 are distinguished by individualized exterior trim and color areas as well as interior upholstery and appointments.
Seven models are available in the Bel Air series. These are the Two-door Sedan, Four-door Sedan, Two-door Sport Coupe, Four-door Sport Sedan, the Convertible, the Nomad and the Four-door, six-passenger Station Wagon.
Series 2100 is composed of eight models. These include the Two-door Sedan, Four-door Sedan, Two door Club Coupe, Two-door Sport Coupe, Four-door Sport Sedan, Two-door, six-passenger Station Wagon, Four-door, six-passenger Station Wagon, and the Four-door, nine-passenger Station Wagon.
A Two-door Sedan, Four-door Sedan, Utility Sedan and a Two-door,
six-passenger Station Wagon comprise the 1500 series. The Sedan Delivery
is again available for commercial use and not included in the passenger
car line-up.
Exterior Styling
Exterior Styling
Series 2400
Series 2100
Series 1500
Exterior Styling
Chevrolet models for 1957 display a totally new appearance with new colors and new exterior styling, as well as extensive body and sheet metal changes. An integrated look is the styling keynote. The bumpers, grille and other new components embody contours which make them essential elements of the vehicle overall design, without any harsh interruptions of the body lines.
The substantial increase of 2-1/2 inches in length for the sedan and coupe models, the slight decrease in overall height as well as the sweeping horizontal body lines create a low, long silhouette and an even more luxurious vehicle appearance.
Redesigned components include a new hood 1 1-1/2 inches lower at the cowl, with a flat horizontal surface sloping sharply downward at the forward edge to meet the grille. Length is emphasized by the long, horizontal line extending rearward from the hoods over the headlights to the rear fender fins. The front bumper-grille combination as well as the rear bumper, containing the tail, stop and accessory back-up lights, follow the overall styling theme of a completely integrated car.
Seventeen exterior colors are available for 1957, seven of these being new. The colors are grouped into sixteen solid color exteriors and fifteen two-tone combinations. The conventional method of two-toning which specified a roof of one color and the rest of the body and sheet metal another, has been eliminated. Each series for 1957 has a distinctive two-tone treatment.
The new and modern front end design is the result of styling integration of sheet metal, grille and the front bumper. Reproportioned and redesigned, the components all contribute to the prominent impression of vehicle width, length and a lower overall height.
Styled into one unit, the grille-bumper combination consists of three main elements blending into the sheet metal contours. The upper bar extends along the lower hood edge, then arches down to the heavy lower element which is the bumper proper. A lattice pattern aluminum grille screen, featuring long rectangles, forms the background for the central grille bar containing the parking lights at either end and the Chevrolet medallion in the center.
A lower, flatter hood, conforming to the styling theme, is 1-1/2 inches lower at the cowl and retains the some height differential at the forward edge. Twin hood ornaments distinguish the new Chevrolet, replacing the single ornament of previous years. New hood emblems again provide the differentiation between models with six and eight-cylinder engines.
An outstanding note of identification is provided the 1957 Chevrolet by the new twin hood ornaments with overall contours extending the entire length of the hood horizontal surface.
Bright concave depressions at either side of the hood extend rearward to the decorative, non-functional air intakes containing bright metal, rocket shaped ornaments. From the ornaments rearward, the contour is convex, tapering to the cowl as windsplits augmenting the twin air scoop design.
Headlights are spaced 1-3/10 inches farther apart for 1957 and are again recessed under hoods formed by the fenders. The forward edge of each hood is outlined by a bright metal bezel. The upper half of the wide grille, surrounding the headlight, consists of a dull black wire mesh and forms the air intake for the body ventilation system, while the lower portion is purely decorative. This method of introducing air into the body replaces the plenum chamber system of previous models.
The functional and decorative grille-bumper combination is composed of three main elements which blend into the sheet metal contours and contribute to the low, clean-cut lines of the front end styling. The bright metal header bar, attached to the hood, arches to meet the bumper proper. The bumper is a massive element which replaces the lower portions of the fender corners and sweeps under and across the vehicle width. At either end the contour is extended forward, forming massive decorative elements to replace the former applied bumper guards. The grille design features a horizontal center bar, terminating at either end in circular parking lights and, at its center, contains the Chevrolet medallion. The center bar is located on a lattice pattern screen of long horizontal rectangles which fills in the grille opening. The screen is of gold anodized aluminum on Bel Air models and bright anodized aluminum on Series 2100 and 1500.
Located on the forward edge of the hood the word "Chevrolet," in script, above a large flat V identifies the 1957 models with V-8 engines. Six-cylinder models display only the Chevrolet nameplate, in larger script. The nameplates and emblems of Series 2100 and 1500 are in bright metal, while those for the Bel Air series are of gold anodized aluminum.
See Illustration 23 and See Illustration 24
Individual body side moldings again distinguish models of each of the three series. Bel Air vehicles display a large, lance-type molding beginning immediately to the rear of the headlight and arching gently downward along the full length of the car to blend into the rear bumper. At the rear quarter area another molding branches off sharply upward, then horizontally rearward to the fender crown molding. A rolled anodized aluminum panel with a shallow, fluted design, fills in the area defined by the two body side moldings. The gold anodized aluminum Bel Air nameplate and crest are located in this area, at the rear edge of the fender. A bright metal sill molding completes the side trim.
Series 2100 models have the some lance and rear quarter moldings as the 2400 series, without the rear quarter insert panel. The Chevrolet nameplate, in script, is located in the insert area.
Models of the 1500 series feature body side ornamentation consisting of a sash molding which extends diagonally forward and downward from the dip in the belt line to the horizontal rear fender trim. A bright metal Chevrolet nameplate is located on the front fender, just forward of the door.
While providing a distinguishing appearance to each of the three series, the body side moldings also serve to define areas for two-tone color effects.
In addition to solid color exteriors which are available on all models, a distinctive two-tone combination is offered for all models of the three series, with only the convertible excluded.
Bel Air model two-toning provides one color on the roof, and pillars. The second color is used on the lower body, sheet metal rear deck and wheels.
Two-toned models of the 2100 series display one color on the roof, pillars and rear quarter insert area. The second color covers the remaining areas of the vehicle.
Series 1500 two-toning features one color on the roof, pillars, wheels, sheet metal and entire body, except the upper quarters and deck lid, where the second color is applied.
See Illustration 24and See Illustration 25
Front fender crowns extend forward to form functional peaks over the headlights and add to the illusion of length. The forward edge of each peak is outlined in bright metal. Beginning at the forward edge, a windsplit line runs along the full length of the fender crown.
An outstanding note of identification is given all 1957 models by three vertical D-shaped louvers located on the fender side, behind the headlight. The louvers are of gold anodized aluminum on Bel Air models and are painted indentations in the fenders of vehicles of the 2100 and 1500 series.
Rear fender crowns extend horizontally rearward, then sweep back sharply at a reverse angle down to the bumper guard and tail light combination. A wide molding covers the crown of Bel Air models, beginning at the rear window and sweeping down to the tail light. Series 1500 and 2100 models also display a rear fender crown molding which, however, extends only a short way along the fender top.
Wheel openings sweep to the rear for an expression of speed and are framed by flat beads which add massiveness to the appearance as well as strength and rigidity to the fender construction.
New fourteen-inch wheels and low pressure tires are standard equipment on all models. The tires are larger in cross-section, and appear softer and fatter, assuming the proportions usually associated with higher priced cars.
Bel Air wheel disks are entirely new in design. The round central portion of the disk displays three windsplits branching off at equal distances from the familiar Chevrolet medallion which is centrally located on a round, dull black background. Semi-cylindrical contours extending to the wheel rim, complete the wheel disk design.
Hub caps of Series 1500 and 2100 are also entirely new, resembling somewhat the central portion of the Bel Air disk. The identifying Chevrolet medallion in the center is highlighted by three windsplits extending toward the outer periphery. Decorative embossments surround the central element.
The rear end appearance of the 1957 Chevrolet also continues the theme of massiveness and luxury. High rear fender fins provide an impression of width and, together with the ornamental bumper guard and tail light combination, lend the rear end an appearance of prestige, in keeping with the overall styling.
New bumper guards house the tail lights and form the lower portion of the rear fender to continue, as on the front, the integration keynote.
The license plate is again located on the deck lid below the emblem, illuminated by a light in the upper surface of the bumper face bar. Vehicles with six-cylinder engines retain the large Chevrolet medallions as deck lid emblems. Models with the optional eight-cylinder engines display a large Vee and "Chevrolet" in script as the deck lid decoration. Bel Air models feature this ornamentation in gold anodized aluminum, while chrome is used on Series 2100 and 1500.
Station wagon models again have the license plate mounted in a depression in the rear bumper and illuminated by lights incorporated into the applied bumper guards located at either side of the license.
An accessory deck lid trim panel is available on all sedan and coupe models. The horizontally ribbed trim panel, of extruded anodized aluminum, extends along the lower edge of the deck lid, onto the body.
The central portion of the left rear fender crown molding is hinged and swings open sideways to reveal the gasoline filler cap. The door is mounted on over-center hinges, needing no latches to keep it shut. A fuel tank vent, composed of plastic tubing, is incorporated in the gasoline filler pipe, to help prevent overflow on filling the tank.
The massive new tail light and bumper guard combination imparts a look of luxury to the 1957 rear end styling. Continuing from the rear fender crown molding, the large bright metal unit consists of two sections. The upper crescent shaped portion houses the tail, stop and direction signal lights. The lower section functions as a bumper guard and contains provisions for the accessory back-up lights which are deeply recessed in the central portion of the unit. The back-up light extends rearward to accentuate the vehicle length appearance.
The single rectangular license plate light is located at the top
center of the rear bumper face bar, which is restyled with a flat upper
surface and an overhanging crown. The license plate is again mounted on
the deck lid. Station wagon models have lights located in bumper guards
at either side of the license plate.
Series 2400
With the new integrated appearance and a skillful use of
exterior ornamentation, which includes subtle touches of gold, Bel Air
models for 1957 are outstanding examples of luxury in good taste. All
components emphasize massiveness, width and vehicle length, and
contribute to the luxurious appearance of the 1957 Chevrolet.
Series 2100
A versatile group of eight models comprises the 2100 series.
Each model is distinguished by the single lance molding sweeping along
the entire length of the vehicle and the Chevrolet nameplate and wing
molding on the rear fender. Other items of exterior ornamentation
include now hub caps, bumpers, grille, as well as identification
emblems.
Series 1500
Models of the 1500 series, the economy vehicles of the Chevrolet
line, display a quality appearance usually associated with higher priced
cars. The new rear quarter moldings provide a note of distinction for
all four models, and the bright metal windshield and rear window reveal
moldings are included in the exterior ornamentation.
Interior Styling
Interior Styling
Series 2400
Series 2100
Series 1500
Interior Styling
The 1957 Interiors
Chevrolet models for 1957 feature completely restyled interiors which display new seat design and steering wheels as well as entirely new instrument panels. The striking array of pattern cloths and vinyls further compliments the design. Interiors are color-keyed to the exteriors on all 2400 and 2100 series models as well as on the Series 1500 station wagon.
Front seat backrests of all models are reshaped for a more slender appearance and greater passenger comfort. The new design also permits unusual styling effects for the backrest bolster treatment.
New long and slender applied-type arm rests conform to the sleek seat and sidewall styling.
The instrument panel is completely restyled. A deep cove, bright aluminum on Bel Air and painted on Series 2100 and 1500 models, contains all the control knobs. A new instrument cluster, featuring large, full-faced dials is located directly in front of the driver. All models for 1957 have basically the same two-spoke steering wheel with a deeply recessed hub. The two spokes are offset to provide a smart off-center appearance and allow an unobstructed view of the instruments. The radio speaker grille is relocated to the top of the instrument panel.
See Illustration 33 and See Illustration 33B
The new instrument panel, featuring an extremely deep overhanging crown, heightens the impression of spaciousness and sets the styling keynote for the 1957 interiors.
Instruments are installed under a deep, flat hood, superimposed on the instrument panel crown, directly in front of the driver. The hood is framed in chrome on Series 2400 and 2100 models. Full-faced gouges, with red indicators and tell-tale lights for the generator and oil pressure, permit the driver to take readings at a glance. The large, round speedometer, containing the odometer and high-beam indicator as well as the automatic transmission quadrant, dominates the cluster. At the left of the speedometer is the temperature gouge, and at the right the fuel gauge. The radio speaker grille is relocated to the top of the instrument panel crown.
A new feature of the 1957 instrument panel is the illumination provided for all control knobs. Green plastic lenses form the lower surface of the gasoline and temperature gouge housings, through which the light used to illuminate the dials is cost down on the control knobs.
All control knobs are deeply recessed beneath the overhanging crown. The deep set control knobs blend with the distinctive design of the instrument panel. The knobs are all located on massive bezels extending from the panel surface. These bezels are bright metal on Bel Air vehicles and are pointed silver on Series 2100 and 1500 models. The control knobs are black plastic, encased in bright metal on Series 2400 and 2100, and solid black plastic on Series 1500 models. The control knob function is identified by a black escutcheon with white letters. Series 1500 models, however, have plain silver pointed escutcheons.
The cove insert is aluminum with small black squares on Bel Air models, and is pointed silver on vehicles of the 2100 series. The entire cove as well as the remaining portion of the instrument panel is pointed silver on Series 1500 models. A bright metal molding separates the insert from the lower portion of the panel on 2100 series vehicles. A gold-plated Bel Air nameplate, located on the insert at the right, identifies models of the 2100 series. This is replaced by the word "Chevrolet," in bright metal script, on Series 2100 and 1500 vehicles. Controls for the lights and windshield wiper are at the left of the steering column, while the ignition lock and cigarette lighter, or provision for one, are of the right. Accessory radio controls and dial are again located in the center of the panel, directly above the glove compartment. The electric clock, which is standard equipment on all Bel Air models, is located at the right hand side of the panel.
Rear view mirrors of sport sedan models are relocated from the windshield header to the windshield lower garnish molding, providing better rear view visibility. On all other body styles the mirror mounting on the windshield header is retained.
The relocation of the radio speaker grille from the right end to the top center of the instrument panel provides a more ideal distribution of sound as well as a wider dynamic speaker range.
All models for 1957 feature basically the some two-spoke steering wheel with a deeply recessed hub. The two spokes of the new wheel describe a wide arc to create a smart off-center appearance and present an unobstructed view of the instruments.
The steering wheel of Series 2400 models carries the words Bel Air on the hub, while the words Two-Ten identify vehicles of the 2100 series. Both series feature a full circle horn-blowing ring which is replaced by a horn button on Series 1500.
The steering column is a massive unit which blends into the contour of the instrument cluster to become an integral part of the instrument panel styling.
Front seats of all models feature slender backrests. This permits the bolsters or bolster inserts to wrap around to the rear of the seat to heighten the effect of roominess and provide new seat styling. Front seat tracks are also modified to give slight increases in front seat head room of most models.
Armrests for 1957 are the applied type for all models of the 2400 and 2100 series. The Bel Air armrest, considerably longer than the 1956 version, harmonizes well with the interior styling theme and provides a greater measure of support, regardless of the position of the seat. The armrests of Series 2100 models, although shorter, resemble those of Bel Air models. The armrests of both Bel Air and Series 2100 models are oblong in shape, and provide a hand grip for closing the door.
All station wagon models of the 2400 and 2100 series feature
rear seat ash trays for 1957. These are available as a single ash tray
in the front seat back of four-door models, or as dual ash trays, one in
each rear quarter trim panel of two-door vehicles as shown.
Series 2400
Bel Air conventional sedans and the four-door station wagon display similar seat and sidewall trim, which reflects the luxury incorporated into the 1957 models. A nylon-faced, Jacquard weave, cloud pattern cloth covers the cushions and backrests. A new crushed grain vinyl, in light tones, is used on the backrest bolster which is set off by two inserts of dark tone, ribbed, patent leather vinyl. This some fabric forms the cushion bolster. Leather grain vinyl, in light tones, is utilized for all facings and this same fabric, in dark tones, covers the front seat end panels. Bright plastic welts set off the various trim areas.
Sidewall design blends with the luxurious seat trim. The upper and lower panels simulate the dark tone pattern cloth of the seats. The arched center panel and upper portion of the scuff pad are of light tone leather grain vinyl, while patent leather vinyl is used for the scuff pad. Carpeting, front and rear, covers the floors of the sedans, while vinyl coated rubber is used on the station wagon.
An entirely different seat and sidewall design is featured by the sport sedan, sport coupe and the Nomad.
The backrest inserts and the cushion are trimmed in the nylon-faced pattern cloth common to all Bel Air models except the convertible. Light tone leather grain vinyl is used on the backrest, cushion insert, and facings, while dark tone leather grain vinyl covers the front seat end panels. Bright plastic and vinyl welts accentuate the seat trim.
The distinctive sidewalls feature cloud pattern sidewall cloth on the upper panel and the center panel insert. Leather grain vinyl in light tones is used on the center panel, while this some fabric, in dark tones, is provided on the scuff pod.
Light tone pique vinyl is used for the headlining of the sport coupe and sport sedan, while a weave pattern vinyl headlining and bright metal roof bows are utilized by the Nomad. Carpeting covers both front and rear compartment floors of these models.
The convertible features seat and sidewall trim which is basically identical to the other sport models. However the pattern cloth of the backrest inserts and cushions is replaced by a vinyl having a golf ball pattern. The backrest and cushion inserts utilize a vinyl with simulated stitching to provide a ribbed effect.
Sidewalls are covered by the same golf ball pattern vinyl, with leather grain vinyl providing the contrast.
As on other Bel Air models, dark tone carpet covers the
passenger compartment floor.
Series 2100
All models of the 2100 series, except the club coupe, have similar styling of seat and sidewall trim, with the station wagons differing from the other models only in colors and fabrics.
Seats of sedan and sport coupe models use a nylon faced, Jacquard-type, picket pattern cloth on the cushions and backrests. Cushion and backrest bolsters are of light tone ribbed vinyl, while light tone leather grain vinyl is used for the facings and bolster inserts. Dark tone leather grain vinyl covers the front seat end panels.
Sidewalls feature a light tone nailhead pattern vinyl on the upper panel, picket pattern vinyl on the center panel, and a dark tone leather grain vinyl scuff pad.
Vinyl coated rubber covers both the front and rear compartment floors. Station wagon models differ from the sedans and coupes, in that the pattern cloth of the cushions and backrests is replaced by an Inca pattern vinyl, which is also used on the center panel of the sidewalls. A light tone weave pattern vinyl is used for the headlining.
The club coupe for 1957 again displays an all vinyl, one-of-a-kind interior. Cushions and backrests are of Inca pattern elascofab in dark tones while the bolsters are in light tone leather grain elascofab with ivory horizontal saddle stitching. This same leather grain elascofab is also used for the facings. Leather grain vinyl, in dark tones, covers the front seat end panels.
The center panel and upper insert of the sidewalls duplicate the Inca pattern vinyl of the cushions and backrests. Leather grain vinyl, in light tones on the upper and lower panels and in dark tones on the scuff pad, completes the sidewall trim. Saddle stitching on the lower panel further enhances the door panel design.
Weave pattern vinyl is used for the headlining, and carpeting
covers both the front and rear passenger compartment floors.
Series 1500
The distinctive seat trim of Series 1500 sedans features a new, gray and black, nylon and rayon faced cobblestone pattern cloth, which is used on the cushions and backrests. Black leather grain vinyl forms the backrest bolster, cushion insert, facings, and front seat end panels.
Sidewalls harmonize with the seat trim. Cobblestone pattern vinyl in gray and black is used for the upper panel, while black leather grain vinyl covers the lower portion of the sidewall. Black rubber floor mats cover the front and rear compartment floors.
An optional interior is also available on the sedan models. Silver colored vinyl replaces the black on the bolsters, facings, cushion inserts and sidewall center panels.
The Series 1500 station wagon repeats the seat and sidewall
design of the sedans but in all vinyl materials, and in a choice of two
colors. Cobblestone pattern vinyl, in black and gray or green and gray,
covers the cushion, backrest, and upper panel of the sidewalls. Black or
green leather grain vinyl is used on the bolsters, facings, front seat
end panels, and the lower panel of the widewalls. Black rubber mats
cover the passenger compartment floor, and black or green linoleum is
used on the load space.
Visibility, Size and Roominess
Extensive body and chassis changes, completely restyled sheet metal and bumpers, as well as interior refinements, account for a large number of dimensional revisions.
All models feature an increase in visibility area. With a lower cowl, due to the elimination of the plenum chamber, the opening of the windshield is increased in size along the lower edge. The increase amounts to 75.4 square inches on the sport models which include the convertible, Nomad, sport coupes and sport sedans. Windshields of the other models are 69 square inches larger in visibility area. All other windows remain unchanged.
Overall lengths of the new models have been revised to a universal 200. 0 inches from 200. 8 inches for the station wagons and 197.5 inches for the other models. With the redesigned front end sheet metal and bumper, the front overhang is decreased 32.5 inches. However, the angle of approach is reduced to 21 degrees and 35 minutes. The massive rear bumper increases the rear overhang to 52.5 inches, thereby lessening the angle of departure to 12 degrees and 17 minutes. Wheelbases as well as front and rear wheel treads remain unchanged.
Redesigned chassis components, including 14 inch wheels, decrease chassis heights at the forward end. However the minimum 6. 1 inches under the rear spring front hanger is retained. Lower chassis heights also contribute to a slight decrease in overall height for all 1957 models. All 2-door and 4-door sedan models as well as the club coupe now measure 60.4 inches in height. All station wagons are lowered to 60.6 inches except the Nomad which measures 59. 2 inches and model 2119 which is 62.4 inches. Sport coupes are 59. 0 inches high while sport sedans and the convertible are lowered in overall height to 58. 9 inches. Maximum overall width is also decreased for all models from 74.3 to 73.9 inches.
Front seat adjusters of all models except the station wagons are slightly modified for repositioning the seat one inch to the rear. In addition, a review and revision of all dimensions was made to eliminate differences in specifications between design figures and production car measurements. As a result, front seat legroom dimensions undergo changes, varying from an increase of .84 inch on the sport coupe models to a decrease of .3 inch on the station wagon.
Adjustment of specifications as well as the seat repositioning reduce rear seat legroom throughout the line, varying from a decrease of 1. 7 inches on the Nomad to 3. 5 inches on the nine-passenger station wagon. For the same reason other interior measurements are also changed. Front seat headroom changes vary from a . 1 inch decrease on the sport sedans to a . 64 inch increase of the convertible. Somewhat lesser headroom changes are listed for the rear seat. The shoulder and hip room also change in many instances, with a slight decrease in roominess on some models and an increase on others.
A detailed listing of dimensional changes for all models will be
found on page 114, in the Appendix.
Ventilation Body and Sheet Metal
A completely new and higher capacity ventilation system, a deeper windshield and a roomier engine compartment are the results of related structural changes in the cowl assembly and the front end sheet metal. The reshaped hood panel is also new in structure and more effectively counterbalanced. The basic body structure, except for the cowl, is unaffected by the extensive appearance changes.
The ventilation system is completely new, redesigned to keep pace with the styling changes. The plenum chamber of previous models is eliminated. Air is introduced into the system through screened openings located in the fenders above each headlight, then flows rearward through round ducts extending under the fenders, through the skirts and into each side of the dash panel. The system has a water separation feature, consisting of a sharp dip and a metal grain tube at the front portion of each duct, to collect and drain off any water which may enter.
One of the outstanding new features of the ventilation system is the substantial increase in air flow volume at highway speeds, nearly 22 per cent over the previous design. At 60 miles per hour this system is capable of introducing 746 cubic feet of air per minute into the vehicle interior, as compared to 611 cubic feet per minute with the plenum chamber system. The water drainage capacity is also increased.
Another feature is the comparatively high level of air intake. The screened intakes are located 35. 9 inches above the ground, only 6 inches lower than the former plenum chamber intake.
With the elimination of the double -walled plenum chamber, the body cowl and dash assembly is completely redesigned, the cowl being approximately one inch lower at the centerline of the body. Only four main panels comprise the body forward construction. The new dash panel is rigidly braced by dash legs which extend down to the frame. In turn, the dash panel reinforces the upper shroud panel which forms the upper section of the cowl. Lower shroud panels, reinforced at the hinge pillars by channel section braces complete the structure.
The completely new styling as well as the new ventilation system also account for numerous hood and sheet metal revisions. Restyled fender contours require new fender skirts which must also accommodate the air ducts. The two-piece welded skirt forms a wheel well, providing considerable usable space immediately behind the wheel and under the fender. The air ducts extend rearward from the headlight, through the vertical portion of the skirt, and into the enlarged engine compartment.
The new hood construction is an indication of the quality designed into the 1957 Chevrolet. To provide the necessary rigidity to its broad, flat surface, the hood is braced by a sturdy arrangement of channel section reinforcements and cross bracing, to minimize any deflection.
The entirely new front bumpers feature redesigned frame-to-bumper attachments. An additional diagonal brace, extending from frame to bumper wraparound, replaces the fender bracket attachment of previous years.
Ventilation system air intakes are located beneath headlight hoods. The actual intakes surround only the upper portion of the headlamp, but the grille design is continued around the lower portion as well, for a symmetrical appearance.
The relatively high location of the air intakes, away from low lying dirt and heat of the road, assures a comfortable supply of air to the vehicle interior. In addition, the forward position and scoop-like design of the intakes provide, at high vehicle speeds, a greater volume of air than that obtainable with the former plenum chamber design.
Large round louvered outlets, located at either side of the dash, beneath the instrument panel, are designed for an even distribution of the larger quantities of incoming air available with the new ventilation system. Outlets are controlled by knobs at either end of the instrument panel. Control knobs are relocated to the heater control panel when the optional air flow heater is specified.
The gear type hood hinges are engineered to reduce the initial effort required to raise the hood, and to maintain a more constant effort requirement throughout the hood travel.
The geometry of the hinge is rearranged to increase its mechanical advantage, and the spring is placed outboard, under the fender, for a cleaner engine compartment appearance. The rigid flanged channel section hood rear reinforcement, to which the hinges are attached, assures uniform hinge action.
The new hood panel is somewhat wider at the forward edge, and is
considerably narrower at the rear, with sides almost parallel to each
other. The flat hood structure is extremely rigid, however, featuring
channel section stiffening members along its sides, as well as a center
brace extending the full horizontal length. These longitudinal braces
join a wide flanged channel section hood rear stiffening member, to
which are attached the hinges. At the forward portion of the hood, the
side braces join another channel section reinforcement. The hood
horizontal support is completed with the radiator upper baffle, which
joins the three longitudinal braces. A massive lock plate, bolted to the
hood forward reinforcement, projects downward to the hood forward edge.
Tie rods, extending upward and rearward, from the lock plate to the
forward reinforcement, minimize any hood deflection in a vertical plane.
Engine and Chassis
Three basic engines, including a new 283 cubic inch displacement V-8, are offered to meet the widely varying power requirements of the motoring public. Ratings range from 140 horsepower in the standard Blue Flame six to 270 horsepower in the competition version of the new 283 cubic inch V-8. A new, highly responsive fuel injection system extends this range to a high of 283 horsepower. The Blue Flame six, the optional 162 horsepower Turbo-Fire 265 V-8 and all four 283 cubic inch engines are performance keyed to five transmission-axle combinations so that a total of seventeen compatible power trains are now available.
The new 283 cubic inch V-8 engine, having a . 125 inch larger bore than the Turbo-Fire 265, is available in four versions which differ as to carburetion, exhaust system, camshaft, and valve train. Compression ratios range from 8. 5-to-1 on the Turbo Fire 283 to 10.5-to-I on the competition version with fuel injection.
The two-barrel Turbo-Fire 283 is rated at 185 horsepower and teamed with either Powerglide or the new Turboglide transmission. The Super Turbo Fire 283 with four-barrel carburetor and dual exhausts has a compression ratio of 9.5-to-1 and a gross output rating of 220 horsepower. It is offered with any one of three transmissions the standard three-speed synchromesh, Powerglide or Turboglide.
All high performance engines, the "Corvette" V-8 is, are based on the new 283 cubic inch displacement. The dual four-barrel "Corvette" V-8 is rated at 245 horsepower, has 9.5-to-I compression ratio, hydraulic valve lifters and dual exhaust system, and is available in combination with every transmission offered, including the close ratio three-speed synchromesh. The competition version of this engine is rated at 270 horsepower, and has a competition camshaft and a high-speed valve train. It is teamed with the standard three-speed or the close-ratio three-speed transmission so that its high output potentialities can be fully realized.
During the model year, a fuel injection system will replace the dual four-barrel carburetors. Priority will go first to the special competition engine featuring a 10. 5-to-I compression ratio and raising its rating to 283 horsepower. As availability permits, fuel injection will be installed on the regular "Corvette" V-8 engine increasing its output to 250 horsepower.
In addition to increased performance capabilities, the new V-8 engines share many significant new features which contribute to greater efficiency and durability. The standard Blue Flame six, while basically unchanged, is made even more dependable.
Engine serial numbers for both six-cylinder and V-8 are discontinued. A new schedule of letters and numbers, stamped in the same location, identify the engine manufacturing plant, month, day of assembly, and type of engine.
NEW 283 CUBIC INCH V-8 ENGINE.
The new 283 cubic inch displacement V-8 has many advanced features designed to bring improvements over previous V-8 engines in virtually every characteristic. These range from freer breathing, more accurately timed and more uniform mixture burning, to improved lubrication and greater overall durability.
Cylinder head inlet ports are increased in size, making it possible for the engine to take in large quantities of fuel-air mixture more rapidly. Exhaust ports are also larger and, when complemented by the ram's horn type exhaust manifolds, allow more complete expulsion of burned gases. The result is freer breathing and more efficient operation.
Spark plug electrodes are located so that they protrude farther into the combustion chamber, resulting in shorter flame travel and more uniform burning of the combustion mixture, for a gain in mechanical octane numbers. The combustion chamber contour, at the spark plug location, provides a small boss so that the spark plug will remain flush with the combustion chamber wall and thus prevent deposit build-up at the spark plug threads.
New metal heat deflection shields, installed between the spark plug wires and the exhaust manifold, protect spark plug wires and boots from the heat of the manifold.
The cylinder block top deck is more uniformly thick to minimize local stresses. With the new arrangement, head bolts are more firmly anchored, and cylinder bore distortion is minimized.
Front and intermediate main bearings are .0625 inch wider than on V-8 engines of the previous model year, providing longer bearing life through reduced unit load.
The piston second compression ring is designed with the inside bevel in the lower position instead of at the top. This results in balanced pressures behind the ring, with better compression and oil control characteristics on engine overrun and high vacuum conditions. The combination expander and spacer for the oil control ring is redesigned and made of stainless steel, replacing the former heat treat hardened, drawn steel part. The new expander-spacer lends itself to closer manufacturing tolerances and results in improved oil control. See Illustration 51
In place of the former metered pressure oil system, oil is supplied to the valve lifter galleries under full pressure, resulting in improved filling of the hydraulic valve lifters and reduced possibility of oil aeration at high speeds. Both the hydraulic valve lifters, and the mechanical lifters which are used exclusively on the highest output version of the 283 cubic inch engine are designed to meter the oil supply to the upper valve train. The full-flow oil filter is continued as a regular production option.
An improved oil baffle covers the surface of the inlet manifold exhaust crossover passage to minimize the possibility of carbonization of oil in the valve lifter compartment.
A new camshaft with a higher design lift for both intake and exhaust valves is used on all 283 cubic inch engines, with the exception of the competition "Corvette" engine. The new can-1 contours account in large measure for the high output. Idle stability is improved through a reduction in valve overlap. Higher capacity valve spring and damper assemblies are used to conform to the higher cam lift. The spring dampers now reduce valve train noise and improve the performance of the valve operating mechanism.
Connecting rod bearings and the front and intermediate main bearings of both "Corvette" engines are of a premium type continued from mid-season 1956. The new bearings are steel-backed aluminum alloy material with a thin lead-tin-copper overlay, and possess excellent ductility and score resistant properties, having from two to three times the life of former high performance engine bearings.
A new semi-centrifugal clutch is introduced for use in 283 cubic inch V-8's with synchromesh transmissions. Due to the increased pressure plate load at high engine speeds, the clutch slippage is minimized, resulting in reduced clutch fade. An improved clutch is used with the standard six-cylinder engine and Turbo-Fire 265.
A new distributor, used on all 283 cubic inch V-8 engines except the "Corvette" versions, permits ,accurate point settings to be made while the engine is running.
A greater quantity of hotter air is supplied to the automatic choke of the new engine through the use of a tube pressed into the center takedown chamber of the exhaust manifold. The increased volume and higher heat, in combination with a recalibrated choke spring which controls the choke valve, results in smoother operation and increased fuel economy on cold engine starting. A stove cast into the side of the manifold was used on previous V-8 engines. Restarting of the two-barrel Turbo-Fire 283 engine after a short run is facilitated by a new torsion spring which prevents the choke plate from completely closing when the engine is still warm and the choke spring cooled off.
Triple filtering of fuel is provided by the addition of a new highly efficient fuel filter which supplements the filter mounted in the fuel tank and the filter screen built into the carburetor. The new filter, which has a removable sediment bowl for clean-out, is mounted adjacent to the carburetor.
The dual exhaust system is equipped with a new balance tube which equalizes flow of spent gases through both mufflers throughout the entire operating range. The tube connects the right hand and left hand exhaust pipes, and passes around the front of the oil pan. In addition to providing better expulsion of exhaust gas and lower back pressure during engine warm-up, corrosion of the right hand muffler and tail pipe is reduced by dispersion of moisture in the system.
See Illustration 52- Engine RPM Chart
TURBO-FIRE 265 V-8 ENGINE. The greatly improved Turbo-Fire 265 continues in availability from 1956, and incorporates all the features of the new 283 cubic inch engine, which result in improved performance and greater durability. The improved higher capacity clutch, used with the standard six cylinder engine, is also used with the Turbo Fire 265 synchromesh combination.
REGULAR PRODUCTION SIX-CYLINDER ENGINES have an improved starter, a more reliable fuel system, and a higher capacity clutch. The carburetor and air cleaner are also revised to accommodate the lower hood. The starting motor assembly is completely enclosed to protect the solenoid from accumulations of road dirt that could interfere with its operation. Greater efficiency in solenoid operation is reflected in the current requirement which is reduced 36 per cent.
A new fuel strainer is added to the carburetor at the fuel inlet to supplement the filter in the tank. The strainer assures cleaner fuel thus reducing the possibility of carburetor flooding due to the entry of foreign matter.
Improved clutch facing materials, both the molded and woven now used interchangeably, have a higher burst strength and greater life expectancy. Plate pressure is also increased. A slight reduction in facing thickness permits installation of the diaphragm spring with a slightly conical shape. The result is approximately seven per cent higher pressure on the driven plate. For smoother operation, two additional spring dampers are added to the driven plates used with overdrive transmissions.
The carburetor and air cleaner are redesigned for lower overall height. The carburetor air horn is shorter and has a larger diameter. The oil wetted air cleaner is flatter and is now secured to the carburetor by means of a center stud replacing the former clamping method. Other changes necessitated by the lower hood line are a reshaping of the radiator upper tank and moving of the water inlet to one side of the tank from the former center position.
See Illustration 53 and See Illustration 54
Cylinder bore distortion resulting from localized stresses in the V-8 cylinder block are minimized by increasing and more evenly distributing the thickness of the top of the block. Formerly the cylinder head hold-down bolts threaded into bosses integral with the cylinder bore walls, which permitted the possibility of bore deflection when the bolts were drawn up tight. In the new design the cylinder head bolts are anchored firmly in the heavier cylinder block top deck, and extend down into the water jacket, thus carrying the gas pressure loading on the cylinder head into the cylinder block structure, eliminating the need for bolt bosses on the cylinder bare. The hold-down bolts are self-sealing and threads are coated with a sealing compound to further insure watertight connections.
See Illustration 55 and See Illustration 56
Performance and efficiency are improved through larger inlet and exhaust ports in the now V-8 cylinder heads which increase the ability of the engine to take in large quantities of air-fuel mixture for efficient combustion, and accelerate the exhaust of burned gases with a minimum of restriction. The overall height of the cylinder head is increased to provide the added space requirements of the enlarged ports.
More complete cylinder scavenging of V-8 engines is obtained through new streamlined ram's horn type exhaust manifolds. The now manifolds have larger gas passages which gradually increase in cross-sectional area, from the inlet port at the cylinder head, to the outlet which terminates in a center takedown. The manifolds are designed to rush spent gases from each cylinder with equal freedom from back pressure, complementing the enlarged exhaust ports in the cylinder heads.
An improved attachment of exhaust pipe to manifold results in quieter operation and greater durability. The new joint has an inner sleeve around which a formed asbestos packing is placed. A new three-bolt pattern sliding flange bolts to the exhaust manifold, and pulls the exhaust pipe up tightly, compressing the packing and forming a sealed connection. The attachment on previous engines utilized a welded exhaust pipe flange secured to the exhaust manifold by two bolts.
Lubricating oil under full pressure is supplied to the valve lifter oil galleries of V-8 engines. Improved filling of the hydraulic valve lifters and reduced possibility of oil aeration is realized at higher speeds. Oil flow through the hollow push rods for rocker arm and valve lubrication is regulated by a modified valve lifter oil control valve.
In previous V-8 engines a milled slot on the outer diameter of the camshaft rear journal metered the amount and reduced the pressure of oil which passed from the main oil gallery to the galleries, via two drilled holes in the camshaft rear bearings. In the new system, the drilled oil passage from the main gallery intersects the annulus under the camshaft rear bearing. Thus oil under direct pressure is supplied to the valve lifter galleries, which are also connected to the annulus through drilled passages. Incorrect installation or turning of the camshaft rear bearing, therefore, can no longer cut off the oil from the galleries. The milled slot in the camshaft journal is no longer required.
The mechanical valve lifters used in the competition "Corvette" engine likewise are modified to control the amount of oil to the hollow push rods for rocker arm and valve lubrication. The oil passage formerly located in the lifter body annulus is raised to the upper section of the lifter body. Full pressure oil from the lifter gallery is reduced in pressure and enters the new orifice through a controlled clearance between the outer diameter of the lifter and the lifter bore.
A new advanced design distributor is used on both the Turbo Fire 283 and Super Turbo Fire 283. Greater accuracy of distributor point gap setting is maintained throughout the entire operating range of the engine, as a result of transposing the breaker point plate and the governor weights. This places the breaker points directly above the shaft bearing, thus minimizing fluctuations in the gap setting due to wear of the bearing or any movement of the shaft. The addition of a cam lubricator, which consists of a lubricant-saturated wick secured to the breaker plate by a nylon clip, also aids in maintaining point gap setting. The, new lubricator reduces the possibility of scoring of the cam, and will last for the life of the breaker points. An access door is provided in the distributor cap for setting the breaker gap when the engine is running.
The starting motor solenoid, solenoid plunger, and linkage of both six and eight-cylinder engines are now fully enclosed in the redesigned pinion casting to provide a completely enclosed starting motor assembly for better engine starting. The solenoid has been redesigned to provide a more efficient unit. The new solenoid is smaller, with a smaller jump spring and overrunning clutch. Current requirements are approximately 35 amperes, compared to the former demand of 55 amperes. In the previous design, the solenoid was bolted to the side of the starter frame, and the exposed plunger and linkage were subjected to the accumulation of foreign matter. The basic design of the starting motor remains unchanged.
When the Turboglide transmission is used the starting motor is attached directly to a pad on the cylinder block, which improves the dimensional relationship between the starter and flywheel ring gear. In synchromesh units, the starter is mounted on the clutch housing, and the Powerglide starter mounting is on the flywheel housing, as in previous models.
Clutch slippage, with resultant generation of heat and clutch fade, is minimized by increased pressure plate load at higher engine speeds through a new semi-centrifugal clutch. Three floating rollers, installed between and equally spaced around the outer diameters of the clutch cover and pressure plate, exert a direct load on the pressure plate through a rolling wedge action when engine speed is increased. The advantage of a light initial clutch pedal effort is retained at low engine speeds, and high pressure plate loading and fast clutch lockup, for high engine speed and high speed gear shifting are provided by centrifugal action of the rollers. Since the rollers are independent of the clutch release levers, clutch lash and the clutch release bearing are not affected. The semi-centrifugal clutch with a premium high burst facing driven plate is regular equipment on all engines with one or two four-barrel carburetors and synchromesh transmissions.
Faster filling of the fuel tank with a minimum of spillage is provided by the addition of a new pipe which extends from the top of the gasoline tank to the top of the filler neck. In the previous design the displaced air had to force its way out against incoming gasoline, causing turbulence in the tank and filler neck, resulting in a slow filling rate and possible gasoline overflow.
The fuel filler cap is redesigned to prevent loss of fuel when
cornering or parking on grades with a full tank. New air passages in the
gasket and cap are used to vent the tank, replacing the former
depression in the top of the filler neck.
Ramjet Fuel Injection
See Illustration 63 Chevrolet V-8 With Ramjet Fuel Injection
Chevrolet Ramjet Fuel Injection is an entirely new, highly efficient system for supplying a precisely controlled air and fuel mixture to each cylinder of the engine. Among its advantages are faster response to the accelerator and a resulting sense of greater smoothness, both during engine warm-up and under normal operating conditions. Starting is quick and positive, even in severe weather, and smoother idling and low speed operation, together with greater overall fuel economy, is obtained.
Carburetors and their various disadvantages are eliminated. For instance, fuel atomized by air passing through the carburetor venturi, is carried all the way from the carburetor, through the intake manifold, to the intake ports at each cylinder. This makes it necessary to provide intake manifold passages large enough for easy breathing, but small enough to maintain adequate air flow velocity at idle so that the fuel will not settle out and upset the proper mixture ratio. Furthermore, carburetors must be heated to help vaporize the gasoline and to prevent the formation of ice in the carburetor air-fuel passage on cold starts due to the refrigerating action of the carburetor venturi and the atomization of the fuel. The heat required expands the incoming air, making it less dense, causing loss of power.
On the other hand, the Chevrolet Ramjet Fuel Injection system supplies fuel under pressure right up to the cylinder head intake ports through individual fuel lines. Separate passages are also provided to supply clean air, unencumbered by gasoline vapors, all the way to each individual cylinder head intake port. Here the fuel, finely atomized by the injection nozzles, mixes thoroughly with the fast moving air and is drawn into each combustion chamber, thus providing precise and uniform cylinder-to-cylinder distribution. Because fuel is vaporized at the cylinder head intake ports, and the incoming air does not pass through a venturi of the carburetor type where refrigerating action takes place, the induction system does not require heat to prevent icing or help atomize the fuel. As a result, the incoming air is not subjected to external heat and a larger quantity of air is drawn into the combustion chamber. Volumetric efficiency is thus improved and engine power increased.
In broad principle, the operation of the Chevrolet Ramjet Fuel Injection system is simple. The accelerator controls the volume of air admitted to the engine. A mechanism of the fuel injection system continuously measures the volume of incoming air and automatically meters the precise quantity of fuel to be mixed with the air. Other mechanisms enrich the mixture for acceleration, hill climbing and warn-up, and also insure instantaneous delivery of fuel to the nozzles for starting, provide for smooth engine idling, and cut-off fuel when coasting downhill.
The system includes specially designed components, such as an air metering system, fuel metering system, and fuel nozzles. The one-piece cast iron intake manifold and engine cover used on carburetor model Chevrolet engines is replaced by two separate aluminum castings. The lower casting forms the top cover of the engine, while the upper contains the air passages and mounting for the air metering and fuel metering systems. Other new components include an auxiliary fuel filter, a special ignition distributor which drives a high pressure fuel pump through a flexible drive, and a new electric choking system for cold starting.
See Illustration 65 - Air Intake
Outside air for the engine is routed through an air cleaner, where dust and foreign matter are filtered out, and then passes into an air meter, the intake manifold, cylinder head, and combustion chamber. The entrance to the air meter is through a venturi or narrow passage. This passage also has a small opening leading to a vacuum tube. As the outside air rushes into the engine through the venturi, it tends to draw the air out of the tube, which creates a vacuum in the tube. The degree of vacuum is an accurate measure of the volume of air being drawn into the engine. A large volume of air creates high vacuum in the tube, while a small volume of air results in low vacuum.
A fuel meter is used to supply and regulate fuel to the engine. The regular engine fuel pump sends fuel through a fine filter and into a reservoir in the fuel meter housing. The quantity of fuel in the reservoir is maintained at a fixed level by a float controlled valve. Another fuel pump, submerged in the reservoir fuel, is driven by the ignition distributor through a flexible cable. Fuel under high pressure from this pump passes into a central passage where it must lift a ball check before flowing through a series of small holes into a metering chamber. At this point the fuel can go either to the injection nozzles at the intake ports, or back to the reservoir, depending upon the position of a plunger. When the plunger is raised, fuel flows back to the reservoir. As the plunger is lowered, a portion of the fuel flows to the injection nozzles and the remainder returns to the reservoir. The ball check in the central passage permits fuel to flow from the pump when fuel pressure is about 15 pounds or higher so that any vapors which may have formed are compressed back into a liquid.
See Illustration 67 Right Amount of Fuel to Match Air Flow
As the incoming air passes through the venturi and is measured, it sends a vacuum signal to a main control diaphragm in the fuel meter. Depending upon the amount of vacuum, the diaphragm meters fuel by raising or lowering the plunger through a lever, thus delivering with high accuracy the precise quantity of fuel required by the engine for the volume of air being used.
All levers in the fuel metering system are counter balanced so that their movements are unaffected by their own weight. Lever positions are determined only by forces exerted by the sensing devices.
See Illustration 68 High/Low Air and Fuel Flow
See Illustration 69 Fuel Mixes with Air and is Drawn into the Combustion Chamber
The intake manifold has eight individual passages, called ram pipes, one for each cylinder. The fuel injection nozzles are mounted in plastic insulators in the lower part of the intake manifold, near the cylinder head intake ports. As the inlet valves open, fuel spray from the nozzles, which has mixed with the onrushing air, enters the combustion chamber where it is compressed and ignited in the same manner as in a conventional carburetor system. A throttle valve, controlled by the driver through the accelerator, determines the quantity of air, and as previously explained, the quantity of fuel supplied to the engine.
So that the amount of fuel injected is determined solely by the fuel metering system, and not influenced by variations in vacuum, the nozzles are designed to inject fuel into atmospheric pressure at all times. This is accomplished by supplying air from the air cleaner to a small chamber in each nozzle. The fuel injected from a small orifice passes through this chamber, and out a small opening to the intake port.
The arrangement has the added advantage of assuring a consistently accurate fuel air ratio for idling the engine. The volume of air passing through the chamber, although smaller when compared with the volume flowing through the intake manifold in normal driving, constitutes a major share of the air used by the engine during closed throttle or idling conditions.
See Illustration 70 Fast Acceleration
The movable pivot in the fuel metering system is connected by a rod to a fuel enrichment diaphragm, and is normally held in a position which provides maximum economy of operation. The enrichment diaphragm is controlled by vacuum created when air rushes past the opening at the throttle valve. When the throttle valve is partially opened, air rushes through the small space of the opening on its way to the engine, and tries to draw air out of the enrichment vacuum tube. The resulting vacuum in the tube is strong enough to hold the diaphragm back against the opposing force of a spring. This holds the movable pivot in the fuel economy position.
When fast acceleration or more power is called for, the driver presses on the accelerator which opens the throttle valve wider. The incoming air now has a larger opening to pass through, and therefore draws less on the enrichment vacuum tube, reducing the vacuum. The spring now overcomes the reduced vacuum force and moves the diaphragm out. As a result, the movable pivot is pushed toward the end of the lever, moving the plunger down. Therefore, fuel return to the reservoir is reduced and fuel flow to the injection nozzles increased. The richer mixture gives increased power for fast acceleration.
See Illustration 71 Easy Cold Starting
For fast engine starting, it is necessary to get fuel to the nozzles quickly when the starting motor is turned on. Since it would take from 20 to 30 seconds at cranking speed for the fuel pump to build up enough pressure to unseat the ball check, a solenoid is used to open a direct fuel passage to the nozzles.
When the starting motor is engaged, the solenoid, which is automatically energized at the same time, forces a solenoid link upward. This, in turn, pushes the starting lever which forces the plunger down, unseating the ball check. Fuel then is routed directly from the fuel pump to the nozzles. The solenoid is de-energized when the driver releases the key-turn starting switch. See Illustration 72
After starting and during warm up, it is desirable to furnish slightly richer fuel mixtures than would normally be supplied. This is accomplished by changing the position of the pivot in the fuel metering system to call for more fuel. The fuel enrichment system and an electric choke are used for this purpose. The enrichment vacuum route from the air meter to the fuel enrichment diaphragm passes through the electric choke housing. On cold starts, vacuum in the housing pulls a check ball upward against a seat, cutting off the vacuum to the enrichment diaphragm. As a result, the spring moves the pivot toward the end of the lever, moving the plunger down, routing fuel to the nozzles. In the choke housing the vacuum is then applied to the bottom of a piston. At the top end, the piston is linked to a thermostat heated by an element which carries electric current whenever the ignition switch is on. As the thermostat is heated, it relaxes and allows vacuum to pull the piston downward. In its lowest position the piston pushes the check ball off its seat, returning the fuel enrichment system to normal operation. See Illustration 73
The electric choke also controls linkage which holds the throttle valve slightly open for fast engine idling after cold starts. As the thermostat heats up, the linkage and engine idle speed return to their normal settings. See Illustration 74
When coasting downhill or decelerating from higher engine speeds, an automatic fuel cut-off system stops fuel waste and discharge of exhaust fumes containing unburned fuel. Other gains are quiet engine operation and the elimination of exhaust sputtering. See Illustration 75
When going downhill with the foot off the accelerator, the
throttle valve is closed, but the engine, being pushed by the vehicle,
tries to pull in large quantities of air. This creates an unusually high
vacuum at the closed throttle valve. This vacuum is used to send a
signal, through a tube, to a diaphragm located above the high pressure
fuel pump. The high vacuum a connecting link opens a and discharges the
fuel reservoir. As a result, all of the fuel from the pump is discharged in
fuel reservoir, none going to the injection nozzles or engine. The high
vacuum diminishes as the vehicle slows down, closing the valve over the
fuel pump, and fuel again flows to the nozzles. The transition from coasting
fuel cutoff to normal operation is so smooth that the driver and passengers
are not aware of the change.
Electrical System
The chassis wiring harness is divided into separate units, connected by bulkhead connectors making it unnecessary to route electrical wiring through sheet metal. In this segmented wiring system, a bulkhead connector is used to connect the wiring harness on the passenger side of the dash to the engine compartment wiring harness. Another connector on the fender skirt connects the headlamp wiring harness to the engine compartment wiring harness, and a third bulkhead connector on the radiator filler baffle joins the engine compartment wiring harness to the grille harness, which services the front parking lamps, direction signal lamps, and horns.
The bulkhead connector See Illustration 76 on the passenger side of the dash panel has been revised and enlarged to accommodate an accessory junction block which is used with all heater installations. When the junction block is used, it becomes the central panel for all of the electrical services in the car, serving as the terminal point for the tail lamps, stop lamps, dome lamps, instrument panel lamps, and electrical accessories. Each is protected by an individual fuse mounted on the block. When a junction block is not used, the fuses for the various lamp circuits are installed in their respective lines. The headlamp and parking lamp electrical circuits are protected by a single circuit breaker which is located in the redesigned light switch.
Usage of plug-in connectors in the system is extended, and improved connectors, known as multiplugs because they accommodate several circuits, replace many of the connectors which formerly handled single units. As an example, a multi-plug connector is used on the light switch, and when installed, activates all seven terminals of the switch. At the same time it forms a cover over all of the terminal posts, preventing accidental short-circuiting when the electrical system is being serviced. The multi-plug connectors can be installed in one position only, assuring correct assembly.
The battery location is moved to the front of the engine compartment adjacent to the radiator baffle. In this new location, the wider hood opening facilitates battery maintenance.
The fuel indicator gauge on the instrument panel is improved by
an increase in the magnetic field which results in a more accurate
indication of the quantity of fuel remaining in the tank.
Chassis
A softer ride, improved handling and braking, greater structural rigidity and durability are achieved through numerous chassis refinements. While the basic chassis features are retained from 1956, See Illustration 77many major components are affected, among them the tires and wheels, front and rear suspensions, frame, brakes, and rear axle.
A new improved ride is the product of new lower pressure tires, a vehicle weight increase of approximately one hundred pounds, a decrease in unsprung weight, new front and rear springs, and the improved shock absorber valuing. The front suspension deflection rate is increased from 100 to 109 pounds per inch to compensate for increases in the sprung weight.
New 7. 50 x 14-4 ply rating tires require 22 pounds per square inch pressure, two pounds less than the 6. 70 x 15-4 ply tires they replace. The new tires are also 0. 8 inch wider in section, and, along with the new fourteen inch wheels, are one inch smaller in diameter. The 0. 8 inch increase in section width permits use of the lower pressure while maintaining stability and load carrying capacity. The nine passenger station wagon is equipped with 7.50 x 14-6 ply rating tires because of its additional weight.
Ride is further improved, particularly on rough roads, by decreased likelihood of the rear suspension "bottoming" against the chassis frame when severe bumps are encountered.
Rear suspension characteristics are improved by an increase in rear axle clearance, gained by raising the rear spring front mounting and changing to positive spring camber. Both front and rear shock absorbers are recalibrated to conform to the new geometry.
Handling characteristics are also favorably affected by the more nearly horizontal mounting of the rear springs. The new position contributes to the attainment of zero steer at two-passenger load. This has the effect of neutralizing the tendency of the vehicle to understeer (steer out of turns) or oversteer (steer into turns).
Front suspension durability is further increased by a change in the steering knuckle lower control arm spherical joint assembly. In the new design, further advantage is taken of the efficiency and long wearing properties of the non-metallic bearing liner by extending the liner down to cover a greater surface on the ball stud.
Vehicle braking is improved by the reduction of the possibility of uneven pull. This is accomplished in part by equipping the front brake shoes with new, improved facing material that is less sensitive to temperature variations. In addition, the front secondary brake shoe pull-back springs are increased in rate from 40 to 50 pounds. The primary springs retain a 40 pound rate. The lower tension assures that the primary shoes make a positive application before the secondary shoes are actuated. New coil type hold down pin springs on the brake shoes replace the former clip type. The new coil springs provide improved retention of the brake shoes to the flange plates, thus assuring proper alignment of the shoe and drum.
Models with a three-speed or overdrive transmission can now be equipped with a high-pedal power brake option that maintains the brake pedal at a level with clutch pedal height. The unit previously was offered only as an accessory. The high-pedal unit does not replace any of the regular brake system components. It acts as a booster that supplies a definite portion of the brake application pressure, in the same manner as the low-pedal unit option installed on vehicles equipped with an automatic transmission.
Structural rigidity of the chassis is increased by a design change at the front end of the frame. New crossmember-to-sidemember braces are welded to the frame sidemembers, forming a rigid box structure that strengthens the entire forward section of the frame and provides a stronger front bumper attachment mounting.
The rear axle is quieter and its durability is increased through the adoption of higher capacity bearings, improved lubrication, reinforcement of the differential carrier and case, and phosphate treatment of gears.
New higher capacity rear wheel ball bearings replace the 1956 bearings of the same type. Also contributing to the improved rear axle performance are new tapered roller bearings that replace the barrel roller type formerly used at the sides of the differential.
Rear axle lubrication has been improved in two ways. A new drain plug in the bottom of the axle housing facilitates periodic changing of the lubricant to remove contaminants, and a new oil baffle ledge cast into the differential carrier directs the flow of lubricant to the mesh point of the differential drive gear and pinion.
The carrier and case are substantially stiffened by increased thickness and reinforcing ribs at critical areas throughout their entire structures. The differential drive gear and pinion gear are phosphate treated to provide a protective coating, which aids in conditioning during break-in and reduces the possibility of scoring.
Rear axle durability is also favorably affected by the fourteen inch wheels. Lateral thrusts on the smaller wheels, due either to side skids or to Hitting the curb, impose less strain on the axle and wheel bearings, because the moment arm is shorter. 'The moment arm is the distance represented by a vertical line from the center of the axle to the ground. Moreover, with smaller wheels less gear reduction is required, and with the same engine torque the rear-axle torque is lower, thus reducing stress on components.
Because smaller wheels require less gear reduction, the adoption of the new fourteen inch wheel necessitate s new rear axle ratios. A new 3. 36 -to-1 ratio axle is released for use with both the Powerglide and Turboglide transmissions. The 3.55-to-1 ratio axle, formerly used with Powerglide, is now used with the three-speed synchromesh transmission. The 4. 11-to-I ratio axle is again used with the overdrive transmission and the 3.70-to-1 ratio axle with the three-speed close ratio transmission.
Vehicle handling is improved by changing the mounting of the rear springs to a more horizontal position to attain zero steer at two-passenger load, an important handling factor. The new spring position is acquired by raising the spring mounting hole one inch on the front hanger.
Rear springs also contribute to improved ride because of a change to positive spring camber that increases rear clearance and decreases the possibility of "bottoming" at the rear axle. In 1956, the rear springs had a negative camber, or a slightly convex design. The new springs are slightly concave in design. Their increased "bow" drops the rear axle approximately 1/2 inch to accommodate the smaller wheels, while maintaining 1956 chassis height at the rear of the vehicle.
The new 14-inch diameter wheels for 1957 retail a 5-inch rim, but have a newly developed rim contour. The new rim is designed to reduce the possibility of critical air loss from tubeless tires, during severe vehicle cornering. In comparative profiles, the new rim contour appears similar to post designs, with the exception of the drop center which is narrower. The tire outer bead seat retains a 5-degree toper, but now extends farther inward. Therefore, with a broader bead seat and narrower drop center, the seat area, off which the tire bead must be forced before air is lost, is increased.
Larger, higher capacity rear wheel ball bearings provide greater
durability for 1957. The new 3-inch outer diameter bearings are designed
to take greater thrust loads than the 2.8-inch outer diameter ball
bearings of 1956. The new wheel bearings receive lubrication directly
from the axle, unlike the previous sealed-for-life type bearings. The
integral bearing seal is retained to assure the oil tight integrity of
the rear axle.
Transmissions
Automatic transmission
Other Transmissions
Turboglide Automatic Transmission
See Illustration 82 and See Illustration 83
Turboglide, an entirely new automatic transmissions provides features enhancing every facet of automobile performance and comfort.
Combining excellent performance with the absolute smoothness attainable only through the elimination of automatic shifting, Turboglide also features low weight and inherently trouble free design. Turboglide, which features excellent torque multiplication that extends to higher vehicle speeds far surpasses the previous non-shifting automatic transmissions. An added performance boost is provided by a dual pitch stator controlled by the accelerator position. Down hill speed control is now effectively provided through a unique hill retarder.
Forming the basis for many of its functional features, Turboglide embodies a unique hydrodynamic driving principle that eliminates any clutch or band type engagement from standstill to top speed. Three turbines of a five-element torque converter are connected individually to the output shaft through the elements of two simple planetary gearsets. Thus, total torque multiplication is the product of both the torque converter and gear ratios, combining liquid smoothness with the efficiency of gears.
A perfectly smooth torque multiplication transition from standstill to highway cruising speed is the unmistakable identification of Turboglide. This sensation is especially impressive due to the high maximum multiplication of 4. 3-to-1 with the 2-position variable pitch stator at its high or performance angle. With the stator at its low or economy angle, torque multiplication reaches a maximum ratio of 3.8 -to-1, far greater than any previous non-shifting torque converter type transmission.
The Turboglide design readily lends itself to the extensive use of aluminum resulting in spectacular weight savings. The entire transmission housing, for example, is the largest single die-cast part in the world to date, and weighs only slightly more than 15 pounds. The Turboglide transmission option adds only four pounds to the curb weight of a Chevrolet, as compared to 92 pounds added with the Powerglide option.
Turboglide design eliminates the necessity for a low range, because the basic arrangement is inherently speed and load sensitive and capable of unusually broad ratio coverage.
Downhill braking, which in other automatic transmissions is achieved by using low range to drive the engine faster, is more effectively provided in Turboglide by an arrangement which utilizes the converter itself as an energy dissipating device. Kinetic energy transferred to the converter oil supplements engine braking to provide up to 15 per cent greater braking effort, while engine speed is increased less than with Powerglide.
Decreased maintenance is an advantage of the all-clutch design, since the hydraulically applied clutches do not require periodic adjustment to compensate for wear. The absence of any automatic shifting eliminates a host of intricate shift timing devices. Sources of oil leaks are practically eliminated since there is only one tapped hole in the case and no covers exposed to oil under pressure.
Because automatic shift provisions are unnecessary, the hydraulic control system is simple. This permits use of a small cast iron valve body with a heat expansion rate nearly equal that of the steel valve spools. This selection of materials reduces the dirt sensitivity of Turboglide by eliminating the compromise in tolerances required when designing a die cast aluminum valve body to work with steel valve spools under widely varying temperatures. By using similar metals, the clearances remain nearly the same over the entire operating temperature range, and thus prevent the entry of foreign matter.
In every other automatic transmission on the market, the use of metals with dissimilar heat expansion characteristics necessitates the use of large clearances when hot, in order to provide the proper operating clearances when cold. Thus, with these designs possibility exists for foreign matter to hinder proper valve action.
The new selector quadrant sequence, identifying Turboglide equipped vehicles, provides a greater ease in rocking the vehicle in mud or snow.
The Turboglide selector sequence requires that the operator lift the lever only when engaging Park or Hill Retarder. Therefore, the operator need only push the selector lever back and forth between the gating limits to engage Reverse and Drive alternately.
A safety switch operating in conjunction with the selector lever permits starting the engine only in Park or Neutral.
Turboglide, for 1957, gives the driver new freedom from mechanical manipulations. For all forward driving under power, drive range provides the torque multiplication needed at any given speed and throttle position.
For situations other than forward driving, Turboglide offers exceptional control with a minimum number of selector positions, each designed for specific applications.
PARK (P) position provides a positive mechanical, sliding-bolt type lock that will hold the car on the steepest grades. Completely independent of the vehicle service and parking brakes, the parking position is also convenient for holding the car while starting the engine. To apply the parking lock, the car should first be completely stopped, then by lifting the selector lever slightly it can be passed over the gating stop into Park.
REVERSE (R) position may be selected from the Drive position without lifting the selector lever. In this way rocking out of mud or snow is facilitated. A maximum torque multiplication of 3-to-1 at stall is more than ample for all reverse requirements.
NEUTRAL (N) position permits engine operation without driving the car, leaving it free to roll. Also, the safety switch permits the engine to be started with the transmission in Neutral. Park and Neutral are identical in functional characteristics except that Park locks the drive train preventing vehicle movement.
DRIVE (D) range is the position for all forward driving, from starting to highway cruising. Only in Drive range is the high performance stator blade angle available, and it is obtained by depressing the accelerator through a detent-type resistance beyond the full throttle position.
HILL RETARDER (HR) position provides an excellent control of vehicle speed when descending steep grades or throughout any type of prolonged deceleration. Hill Retarder may be engaged at any vehicle speed up to 45 miles per hour, by lifting the selector lever slightly toward the steering wheel and pulling the lever down as far as it will go.
The broad ratio coverage is achieved through an ingenious coupling of the turbines to the planetary elements. It is an arrangement that permits a continuous amplification of the ratio change taking place in the converter.
The mechanical connections between the turbines and the planetary elements are arranged so that any one of the turbines can drive the output shaft. In a sense, the transmission functions as three separate torque converters, each specializing in a particular kind of performance yet working together to effect a smooth transition from the high starting torque at low speeds to the normal engine torque at high speeds.
There is no sensation of one turbine taking over where another left off, because that does not occur. Actually, the individual turbines share the torque delivered to the converter and either multiply it or simply transmit it to the output shaft. The contribution made by each turbine to the total driving torque is determined by vehicle speed and the power output of the engine. The gradual redistribution of the driving load, toward the second and first turbines as acceleration is called for, and toward the second and third turbines as vehicle speed begins to level off, is inherent in the design. No auxiliary sensing devices are required.
The third turbine drives the output shaft by direct mechanical connection through the front and rear planet carriers. The first and second turbines also drive the output shaft, independently of each other, but through gear sets. The first, or starting turbine, drives the output shaft through the rear sun gear and the second turbine through the front ring gear. The reaction members of both gear sets are attached to one-way clutches.
STARTING FROM STANDSTILL is the condition during which the greatest torque multiplication may be produced.
As the torque converter pump speed increases with engine speed, the first turbine receives nearly all of the driving energy available. This causes the first turbine to turn the rear planetary sun gear, forcing the planets to walk around the ring gear, and drive the planet carrier and transmission output shaft in reduction. The ring gear cannot turn backward because of its one-way clutch.
In starting from a standstill torque multiplication is the product of the converter ratio times the 2.67-to-I reduction of the rear planetary gearset.
MID-RANGE ACCELERATION is provided through the progressive and overlapping action of all three turbines as vehicle speed increases.
With vehicle speed increasing from a standstill, the first turbine receives and transmits a diminishing portion of the converter pump output. However, as first turbine output decreases, the amount of energy driving the second turbine increases. As the torque on the second turbine increases it causes this turbine to turn the front ring gear forcing the planet pinions to walk around the sun gear which cannot turn rearward because of its one-way clutch. In this manner, the planet pinions drive the planet carrier and output shaft through the front planetary gearset which has a 1.63-to-1 ratio.
Thus, a liquid smooth torque multiplication transition is provided from the high multiplication, low speed first turbine to the higher output speed and lower multiplication of the second turbine.
The power delivered to the second turbine decreases as the power delivered to the third turbine increases. Because of its direct connection to the transmission output shaft, the third turbine is most favorable for acceleration at higher speeds.
CRUISING performance is obtained when the torque converter reaches the fluid coupling point. With the converter in a fluid coupling condition, all output is through the third turbine which is directly connected to the transmission output shaft.
The first and second turbines are permitted by their one-way clutches to free wheel in the converter oil stream.
At any speed up to 60 miles per hour, an increase in torque multiplication is available by depressing the accelerator through the detent resistance beyond the full throttle position. This changes the pitch of the stator blades to their high angle, which provides a greater redirection of oil entering the pump, to increase the torque multiplication and permit the engine speed to increase for greater power input to the converter. Above speeds of 60 miles per hour at full throttle, the stator freewheels regardless of blade angle, and the converter ceases to multiply torque.
HILL RETARDER may be applied at speeds up to 40 miles per hour to control vehicle forward speed when descending grades.
When the hill retarder position is applied, the multiple disk clutch on the rear planetary gearset ring gear is engaged and all other clutches are released. This drives the first turbine at 2.67 times output shaft speed, while the second and third turbines free wheel. The consequent pumping action of the first turbine creates oil flow in the converter, which effectively brakes the vehicle by increasing engine speed and by transferring kinetic energy into heat in the converter oil. The heat is then dissipated by the engine cooling system.
REVERSE position engages the cone clutch on the front planetary gearset ring gear, holding that element, along with the second turbine, fixed to the transmission case. The cone clutch directly connecting the third turbine to the output shaft via the planetary carriers is also applied.
Starting from a standstill in reverse, the reaction within the torque converter is the same as in drive range. That is, oil flow from the converter pump starts turning the first turbine which turns the rear planetary sun gear.
Consider the rear planetary carrier held by the rear wheels. The rear planet pinions then drive the ring gear in reverse. The rear ring gear then turns the front planetary sun gear which forces the front planet pinions to walk around the locked ring gear and drive the planet carrier and output shaft in reverse,
Turboglide possesses a number of design qualities found in no other automatic transmission. Very light weight, compactness, minimum maintenance requirements, and the complete absence of any automatic shifting devices are the basic design features of the transmission.
Because there are no band-type control elements all driving forces are uniformly distributed about the mainshaft axis for the greatest possible freedom from side loads on shafts, bearings and housing. To eliminate power consuming friction and for extreme durability, principal components of the new automatic transmission are separated by recently developed anti-friction radial needle thrust bearings.
The absence of concentrated stress areas, made possible by the all-clutch design, permits the use of an aluminum alloy transmission case. The 15 pound case and many aluminum components throughout the transmission, achieve a total weight saving of more than 80 pounds as compared with the Powerglide transmission.
Sharply reducing maintenance, the clutches are all self-compensating for wear and require no periodic adjustment. Further, the clutches provide equal holding capacity in either direction of rotation. The absence of automatic shifting in Turboglide provides the basis for long trouble free life and consistently good performance quality. The governor intricate shift timing devices, and many potential sources of oil leaks are eliminated. There are no pressurized covers and only one plugged hole on the exterior of Turboglide. The low number of hydraulic control components permits the use of a cast iron valve body rather than the usual die cast aluminum. By keeping the clearances between valve body and spools to a minimum at all times, the possibility of foreign matter wedging between the valves and the valve body is appreciably reduced.
A substantial performance boost at the operators toe-tip results from a dual pitch stator incorporated in the Turboglide torque converter.
In all torque converters a stator is essential to redirect the oil from the turbine to the pump, in order to accomplish torque multiplication. The amount of torque multiplication, then, depends upon the degree of oil redirection by the stator. On stators with fixed blade angles a compromise must be made, because the angle not only affects the maximum torque multiplication., but also determines the speed range over which multiplication will occur as the converter reaches the 1-to-I ratio of the fluid coupling stage.
The Turboglide dual pitch stator materially reduces the element of compromise through its ability to change blade angle, at driver demand. The dual pitch stator is normally in its low angle position, providing excellent multiplication throughout a broad range of vehicle speeds. Maximum multiplication of 3.8-to-I occurs at approximately 1700 engine rpm, at full throttle from standstill. However, for the highest torque multiplication, by depressing the accelerator through a detent-type resistance beyond full throttle position, the stator blades are switched hydraulically to the high angle. Through detent torque multiplication increases to 4.3-to-1, and engine speed goes up to 2700 rpm. The performance boost is the result of both factors. Torque multiplication is greater and, due to the higher engine speed, horsepower delivered by the engine is greater.
The variable pitch stator consists of twenty air foil section extruded aluminum blades arranged radially around a Multi-piece hub. Each stator blade is affixed to an individual crank arm. The crank arms serve the dual purpose of holding the blades in assembly and engaging a groove in the pitch control piston, to position each blade positively.
The stator hub is made in two halves, and is split on the centerline of the blade cranks to facilitate assembly. The front half of the stator hub contains the overrunning clutch that permits the stator assembly to freewheel when the coupling phase of converter operation is reached. A cylinder bore in the rear hub half contains the blade angle positioning piston.
Further evidence of Turboglide design simplicity and trouble-free operation is apparent when examining the hydraulic control circuit in a typical situation.
Elimination of all automatic shifting requirements reduces the function of the hydraulic control circuit to providing oil under pressure manually controlled clutch applications and stator movements, in addition to maintaining oil pressure and circulation in the converter and supplying oil to one lubrication point.
Oil temperature is controlled by a thermostatic valve, which receives the circulating oil leaving the converter. When the temperature of this oil reaches 180 degrees Fahrenheit the valve completely closes and directs the oil through the heat exchanger incorporated in the bottom tank of the engine cooling system radiator.
To minimize power losses, transmission oil pressure is regulated in proportion to engine torque. A diaphragm exposed to the engine intake manifold vacuum is mechanically connected to a spool valve. This valve modulates oil pressure by varying an opening to the sump, then sending the modulated oil to a pressure regulator valve. Thus, as the engine intake vacuum fluctuates according to power demand, the oil pressure is modulated as necessary to hold the clutches stationary.
As in the Powerglide automatic transmission, there are two oil
pumps in the Turboglide automatic transmission. The larger pump is
driven by the engine through the torque converter pump cover, and the
smaller pump is driven by the transmission output shaft. With this
arrangement, the larger pump supplies oil pressure when the vehicle is
standing still or traveling at low speeds, and the smaller pump supplies
oil pressure at greater vehicle speeds. The use of a pump on the output
shaft also permits the vehicle to be push-started.
Other Transmissions
In addition to the new Turboglide automatic transmission, the overdrive, three-speed, and improved Powerglide transmissions are continued in availability. Both the conventional and Corvette versions of Powerglide include design modifications resulting in greater durability.
Several 1956 mid-season design changes increase durability of the Powerglide transmission. Three of the changes combine to effect an improved flow of cooling oil over the clutch plates. The feed hole is drilled straight through the input shaft to give two inlet orifices. The number of oil holes in the outside of the clutch hub is increased from six to fifteen. Five equally spaced holes are indexed in three planes for uniform oil distribution.
To prevent end thrust diaphragm action of the clutch flange from restricting oil flow to the plates, six slots are machined across the face of the clutch drum hub. A new anti-friction, radial needle low sun thrust washer is used on V-8 models, and a new spring steel clutch hub thrust washer is used on all models. Use of the needle bearing requires a new selective fit washer in front of the clutch drum. The new washer, with more area in contact, is more durable. The tip chamfer on all Powerglide gear teeth is reduced to improve gear life.
In mid-season 1956, the standard three-speed and overdrive transmissions received a new "cam and roller" detent cover assembly on all passenger cars including the Corvette. Designed to improve "shift feel" and operational dependability, the new mechanism provides greater detent pull-in and hold-in forces, and places less dependence upon the precision of the operator's motions.
The improved detent characteristics eliminate the need for gating of the shifter tube. The slotted washer which served this purpose is removed to permit more freedom in moving the shift lever. In shifting from first to second, for instance, no care need be exercised in passing through Neutral. The cross-over is smoother and requires less conscious effort.
In addition to the new cam and roller detent cover assembly, the standard three-speed transmission has an adjustable cam located in the upper end of the mast jacket. The cam is notched and accessible through a slot in the shift lever housing. In the former design, this adjustment necessitated disassembly for shim replacement.
The close ratio three-speed transmission, introduced on the 1956 Corvette, and the Corvette-type Powerglide are now available in combination with the dual four-barrel carburetor and fuel injection engine options.
The close ratios, 2.2-to-1, 1.31-to-1 and direct are consistent with the performance capacity of the high output engines. Intended primarily for racing, the transmission delivers effective torque multiplication to higher road speeds in first and second gears. Further, because the ratios are closely stepped, synchronizing time for up shifting and down shifting is reduced. These advantages equip the vehicle to meet the high-speed maneuvering requirements peculiar to road racing.
The transmission is basically the same as that used on the conventional passenger car. Design changes in the clutch gear, countergear and second speed gear account for the numerically lower ratios. A new clutch gear bearing, mainshaft rear bearing and synchronizer snap ring increase the capacity of the unit.
The standard three-speed transmission is again available as regular equipment on all passenger cars except those equipped with the two-barrel carburetor version of the 283 cubic inch V-8 engine. The three-speed with overdrive transmission option is continued and is available with the regular production six-cylinder engine, the Turbo-Fire 265 V-8, and the Super Turbo-Fire 283 V-8. The Powerglide automatic transmission option is continued and is available with all engines but the 265 cubic inch V-8, and the Corvette V-8 engines equipped with the special competition camshaft.
The Turboglide automatic transmission option is available in all passenger cars equipped with the new Turbo-Fire 283 cubic inch V-8's, except those with the special competition camshaft.
Available with all four of the Corvette-type V-8's is the three-speed close ratio transmission introduced in mid-season 1956. Corvette V-8's equipped with the special competition camshaft are teamed exclusively with the close-ratio three-speed.
The forks, shift levers and interlock mechanism connected to the
detent cover are unchanged. In the former detent cover design, shift
fork positions were indexed by spring-loaded balls that dropped into
depressions on a cam surface inside the cover. The now cam is formed on
the sides of two flat bell cranks spring-loaded in a scissors
arrangement to bear against rollers attached to the shift forks. Because
the design has less internal friction, operating effort is reduced.
Moreover, the new cams have a wider ramp, or entrance way, into detent
so that the rollers ore actually pulled into place while on the
approach.
Other Extra-Cost Equipment
Radios. Extensively redesigned, Chevrolet radios utilize printed circuits and multi-plugs for simplified internal wiring and reduction of individual connections. Push-button radios are transistorized, providing better reception and extending service life. A more sensitive signal-seeking radio has a more precise method of synchronizing push-buttons with favorite stations.
A transistor in the push-button radio eliminates the need for a power supply transformer and mechanical vibrator. The heavy-duty transistor is extremely rugged due to its simple construction. This current-operated, low-impedance current amplifier is particularly suited for use in conjunction with today's automobile electrical systems. Better reception results from the absence of the characteristic electrical and mechanical hum of the vibrator.
A more sensitive signal seeking tuner can select lower power stations on the combination signal seeking, push-button receiver.
A simplified method of setting each push-button for favorite station selection provides more precise tuning. Setting is accomplished by pulling the push--button out, pressing the automatic selector bar until desired station is tuned in, and then pressing the push-button back into place.
AUTOMATIC ANTENNA. A new radio antenna, installed in the right rear fender, is controlled by a toggle switch on the instrument panel. The switch has three positions, up, neutral, and down. The new antenna, which can be extended approximately 60 inches, has a cut-off feature to prevent overrunning its limit of travel. A matching unit, extended manually, is available for the left rear fender.
AIR CONDITIONING. The air conditioning system is redesigned to provide an easily installed unit which can now operate in combination with the conventional deluxe air heater. A new control panel designed for simplicity of operation makes possible complete control from a single location. The new unit is available as a factory-installed option on passenger cars equipped with V-8 engine and automatic transmission. Ease of installation makes it possible for a dealer to equip any 1957 passenger car with the new air conditioner.
HEATERS. The deluxe heater is redesigned, providing quieter operation and improved circulation within the passenger compartment. All heater controls are conveniently located on a single control panel redesigned for simplicity of operation. The deluxe heater core is now mounted in an opening in the dash, and the blower motor is mounted in front of the dash on the fender minimizing noise in the passenger compartment. An air duct located between the blower and heater core carries either the outside air diverted from the new air intake, or the recirculated air from inside the car, to the heater core.
The recirculating heater, is mounted on a plate which covers the dash opening provided for the deluxe heater.
The method of installing the molding at the bottom of the windshield is revised to ensure ample air velocity from the defroster manifold to the windshield for proper defrosting.
BUMPER GUARD CUSHIONS. See Illustration 94Conical in shape and molded in black rubber, the bumper guard cushions provide an attractive new accessory to protect front end bright metal during parking operations. The cushions are easily installed by removing the existing cover plate on the bumper guards and securing with the integral cushion bolt.
CONTINENTAL TIRE CARRIER. See Illustration 95Redesigned to accommodate the smaller size wheels and tires, the continental tire carrier for 1957 features a new lock assembly which is designed for easier operation and more positive engagement. The tire cover is of a drum type, replacing the formed type which exposed the wheel hub cap. The Chevrolet trademark is attractively located on the flat surface of the drum.
See Illustration 96 and See Illustration 97
In addition to the levers of the conventional heating system which now include controls for the left and right outside air ducts, temperature, and defroster, two additional levers are used. One controls the air conditioner thermostat and the other a valve which regulates air flow through outlet nozzles at either side of the instrument panel.
The right hand air intake duct is fitted with a "Y" to supply outside air to the air conditioning system. The duct can be closed by a lever on the control panel permitting recirculation of air from inside the car.
See Illustration 98 and See Illustration 99
Worm air is more effectively distributed throughout the front and rear sections of the car by the heat distributor, which has been completely redesigned. Wider than the previous design, the new distributor directs a sheet of worm air to the sides of the car, where it deflects to follow the car body providing a thermal barrier between the front seat passengers and the wall of the car, and then passes to the rear compartment. Warm air also passes under the front seats to worm the floor for the comfort of rear seat passengers. The smaller heat distributor used in 1956 had its outlet above the center of the transmission tunnel, and heat diffusion followed the contour of the tunnel.
A new control panel is used with the deluxe heater and groups
all ventilating and heat control levers in a single location. The left
hand lever controls the left hand ventilating duct. The right hand lever
has three positions. When it is in the up position, outside ventilating
air is shut off and the heater functions as a recirculating heater. In
the center position, outside air flows directly through the ventilation
duct into the body for summer ventilation. In the fully depressed
position, all of the outside air is diverted through the heater core.
The 3 position blower switch, and the temperature and defroster levers
are continued from 1956. The regular production ventilator push-pull
knobs under the instrument panel are omitted in deluxe heater
installations.
Corvette
The 1957 Corvette
The Corvette for 1957 features new 283 cubic inch displacement engines, and a stronger, more durable driveline. In addition to the new 220 horsepower regular production engine, three versions of the new optional high performance V-8 are available. New Chevrolet fuel injection is introduced in combination with the high performance engine. The basic chassis and reinforced plastic body continue without change.
The more powerful V-8 engine is available with four-barrel carburetion as regular equipment, or with dual four-barrel carburetion or fuel injectio
