GM Corvette 1963-1982 Repair Guide

Design

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The success of the Corvette is largely due to the lengthy option lists that permit an owner to literally tailor his car to a specific type of driving or competition. For this reason, the engines that power the 1963-1982 models have been offered in six internal displacements and approximately 14 performance levels.

Induction systems for these engines are varied and range from a single four-barrel configuration to "Tri-Power" (three Holley two-barrels), Rochester fuel injection, and the new "Cross-Fire Injection" which consists of two opposed throttle body fuel injection units.

The 327 cubic inch V8 was offered from 1963 through 1968 and spanned a horsepower range of 250 to 375; the latter figure being obtained with fuel injection. The 327, in addition to fuel injection, has used the Carter WCFB and AFB, Holley, and Rochester Quadrajet carburetors.

The stroke of the 327 was lengthened in 1969 and this brought the displacement to 350 cu in. The 350 as found in the 1969 through 1979 Corvettes has been available in horsepower ratings from 165 to 370. It is offered with either a single, four-barrel Rochester or Holley carburetor. The 305 engine used in 1980 California Corvettes only, has the same stroke as a 350 but the cylinder bore is a smaller 3.736". The 305, 327 and 350 engines are collectively referred to as the small block Corvette engines.

The 327 engine was derived from the earlier 265 and 283 Corvette engines, but featured many improvements. The block was a completely new casting and provided stronger main bearing webs. The bottom ends of the cylinders were relieved to clear the longer stroke crankshaft. All 327 and 350 cubic inch engines, except base power plants, are equipped with forged crankshafts. Main bearing diameters were increased from 2.30 to 2.45 inches in 1968.

The large block engines were introduced to provide more torque and more flexible horsepower than the peakier small blocks. The cylinder block is quite conventional, the heads are where the innovation lies. Intake and exhaust valves are canted away from each other for optimum gas flow and port configuration. The seemingly strange angles at which the valves point gave rise to the nickname of "Porcupine" which was applied to these heads when they first appeared on NASCAR racing Chevrolets in 1963.

The large block Corvette engine was introduced in 1965 with an initial offering of 396 cubic inches and 425 hp. The 396 was enlarged to 427 cubic inches with a bore increase in 1966, although the top rated horsepower remained at 425. The 427, optional from 1966 through 1969, was offered in 390, 400, 425, 430, and 435 horsepower versions. Carburetors used on the large blocks included four-barrel Holley and Rochester carburetors and three, two-barrel carburetors. The 427 received a stroke increase in 1970 and became the 454. The "big-block" reached its highest performance rating in 1970 with horsepower output listed at 460 for the rare LS7 engine. Details are scarce as to whether this engine was ever installed in a production vehicle.

Generally speaking, the small and large block Corvette engines are of the same basic design. They feature eight cylinders arranged in a vee configuration. The cylinders are numbered front to rear with cylinders 1, 3, 5, and 7 on the left bank and 2, 4, 6, and 8 on the right, when viewed from the rear. Firing order for both engines is 1-8-4-3-6-5-7-2. Both the crankshaft and camshaft are supported by five bearings. Viewed from the front, crankshaft rotation is clockwise. Lubrication is full pressure, and a gear type oil pump feeds the system through a full flow oil filter. Both the oil pump and the distributor are driven by the camshaft. The main oil gallery pressurizes the bearings via the crankshaft and camshaft. The valve lifter oil gallery provides oil to the lifters which, in turn, feed the rocker arms through the hollow pushrods.

The standard bearer of Corvette high performance models was established, with the 1967 introduction of the 430 horsepower L-88 limited production option engine. This unit was furnished with a Tuft-rided and cross-drilled heavy duty crankshaft, magnafluxed and shotpeened connecting rods with 7 / 16 inch connecting rod bolts, forged pistons with pop-up domes, and aluminum cylinder heads (open-chambered in 1969).

The peak of large block development was reached in 1969 with the ZL-1 engine. This was the basic L-88 engine but with an aluminum cylinder block.

 
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