1955 Chevrolet Press Release Pg. 2 of 2
A result of years of research and hundreds of thousands of miles of severe testing, the valve-in-head V8 carries a compression ratio of 8 to 1 and a displacement of 265 cubic inches. The engine is exceedingly compact with a bore of 3.75 and a stroke of 3 inches. The stroke is the shortest in the industry - a factor which signifies less piston travel per mile and great smoothness. Although Chevrolet has had V8s under experiment since it tried out this design in 1917-19, the "Turbo-Fire V8" entails basic re-design in the last three years. Engineers sought the compactness of a short crankshaft with the power of large displacement. The bore is said to be unusually large for an engine of the "Turbo-Fire V8s" length. The combustion chamber is wedge-shaped to provide virtual total combustion of fuel fed by double-throated carburetor. With a minimum of friction and high thermal efficiency, the economy of operation is said to be exceptional. Manufacturing processes complement the compact design to assure unusually fine balance of working parts. Not only is the crankshaft balanced on a newly developed machine with electronically controlled indicators, but a final balance is achieved after assembly. The last balance test takes place before installation of the oil pan. In the case of the sixes it was necessary to design a side-mounted air cleaner and re-position the fan in order to obtain the low silhouette dictated by decreased hood heights. Simultaneously, added efficiency and quietness have been credited to modifications which include a re-designed water pump, larger fan and a completely new fuel pump that guarantees more constant fuel pressure. The 1955 Chevrolet frame has 50 per cent greater resistance to twisting although 18 per cent lighter. This has been brought about by stiffer frame side members, a re-arrangement of side members and a more strategic placement of engine and body mounts. Side members are 14.5 inches farther apart at the narrowest point and four inches closer together at the rear. Straightening of side members has reduced twisting tendencies created by vertical loads. Before determining the location of the new engine mounts, Chevrolet ran exhaustive tests to fix the areas of least vibration. They then established the mountings as close to these areas as practical. The four-point mounts that supplant the three-point mounts of 1954 models were devised so as not to interfere with the natural balance of the engines, and at the same time prevent uneven distribution of torque reactions. Front mounts are strut-type and attached to brackets on each side of the cylinder block at the lower corners and angle to seats on the frame front cross member. The rear mounts are located between the lower rear edges of the clutch housing and short brackets cantilevered from the frame side members. Rubber insulation is introduced both front and rear. Front mountings make use of biscuit-size rubber pads mounted on a spacing tube. These layers of insulation are both above and below the brackets and frame cross member. The pads between rear brackets and frame side members act in shear during engine roll and essentially in shear for engine support. New three-speed transmissions have more load-carrying capacity and structural durability. The gearshift mechanism has been improved. Previously the shaft was mounted along the steering column. For 1955 the shaft is enclosed within the column, producing a "cleaner" appearance. The overdrive unit available on three-speed transmissions may be locked out if desired. It involves the substitution of the 3.7:1 ratio rear axle with a high performance 4.11:1 axle in addition to the overdrive mechanism. Chevrolet reports the overdrive reduces engine speed by 22 per cent, amounting to 615 fewer revolutions per mile. This can represent considerable saving in gas and oil consumption. Most significant improvement in the Powerglide automatic transmission has been the development of a new low range band of unique, double-wrap design. Downshifts are softer and upshifts smoother. The selector lever is concentric with the steering column and, as an assistance to those unfamiliar with Powerglide, an illuminated quadrant on the instrument panel tells the position of the selector. Ammeter and oil pressure gauges have been dropped from the instrument panel and red warning lights substituted. The glove compartment is now in the center of the panel for the greater convenience of drivers. Another among scores of improvements is the perfect counterbalance of trunk lids and hoods. With this feature, they will remain open at any angle. Another innovation is the angled mechanism which will permit full lowering of rear windows on two-door sedans. Relocation of parts in power steering mechanism from the engine compartment to the steering linkage has improved serviceability. This thought was also in mind when the master brake cylinder was placed under the hood. The brake pedal, suspended this year, gets nylon bushings to eliminate the need for lubrication. Power brakes are optional. The rear axle has greater torque capacity and better oil sealing. Area of the clutch disc has been enlarged one-fifth to provide increased durability. Chevrolet's all-weather air conditioner will be available only with v8s as an option. Mechanism for this impressive comfort feature is located underneath the hood and instrument panel, leaving the luggage compartment clear. Nozzles to expel cool air into the passenger compartment are at ends of the instrument panel. A new push-button radio similar to the one on the
Corvette is a highspot among accessories. The design is particularly appreciated on long
trips when station frequencies vary with geographical locations. The radio is equipped
with a bar which, when depressed, automatically tunes in stations in sequence across the
dial. An intriguing "first" for drivers seeking high performance is a "power package" which can be purchased on V8 models. This includes a four-barrel carburetor and dual exhaust system for a consequential horsepower rating of 180.
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