MISC. SMALL BLOCK INFORMATION:

[] 1955 up until about mid-1959 Valve Covers have staggered mounting holes.

[] 1955-1957 Engines have Oil Pumps with a longer drive shaft to the pump and a pump which sits father from the block.

[] 1956 Full flow oil filtration was introduced, using a paper element filter in a canister that was mounted to a feature that was added to the cylinder block casting and machined for this purpose.

[] 1957 The 283 cubic inch displacement V8s were introduced.

[] 1958 :

(A) Bosses for side motor mounts were added to the block casting and utilized for production mounts. The features for front motor mounts as used in 1955-1957 remained part of the block casting.

(B) The 265 cubic inch engine was discontinued.

(C) The cylinder head valve cover mounting bolt holes were changed from the top row staggered to the straight across. The new valve cover design lasted until the 1987 center bolted style covers.

[] 1960 The first year for Aluminum Cylinder heads which were installed on the Corvette and the only year until 1986. These heads were recalled by the factory because of pores castings and replaced with iron heads. This makes them very rare.

[] 1962 The block's cylinder wall casting was revised to allow four inch bores and the 327 cubic inch version of the engine. Also increased crankshaft stroke 3.25-inch was introduced.

[] 1962 The First Year a Carter AFB carburetor was used in a Corvette.

[] 1964 The First Year a Holley four-barrel carburetor was used on the 327-CID / 375-HP Corvette.

[] 1964-1967 Chevy II motors had spin-on Oil Filters.

[] 1964 through 1972 the Transistorized Ignition was offered on the Corvette.

[] 1966 The First Year a Rochester Quadrajet was used on all standard performance small-blocks.

[] 1968

(A) The main journal diameter was increased from 2.30 inch (small) to 2.45 inch (medium But most often referred to as" Large Journal" )

(B) The connecting rod journal diameter was also increased from 2.00 inch. to 2.10 inch. This allowed the use of cast iron crankshafts as the previous parts were made of forged steel.

(C) The rod bolts were changed from 11/32 inch diameter to 3/8 inch.

(D) Oil Filter bosses on all blocks were tapped with 5/16-inch threads. The canister/sock style oil filter was now converted to use spin on filters.

(E) The oil fill location was moved from a tube on the front of the intake manifold to a cap on either side valve cover. 1968 and earlier or there about Valve covers have no holes for PVC or Oil fill caps.

(F) The first year of production to use Accessory Mounting holes in the cylinder heads.

[] 1968 through 1971 a change over from flap type to peg type Intake Manifold valley seals were introduced.

[] 1969 Chevrolet changed from the short water pump to the long water pump.

[] 1970 was the first year for the Screw-in Rocker Arm Studs and push-rod guide plates.

[] 1982 Cross-Fire fuel injection system was introduced on the L83 Corvette engine.

[] 1982-On GM has introduced several metric series starters including one for the 305-CID.

[] 1986 The rear main seal was changed from the 2-piece rubber design to a 1-piece rubber design that used a mounting appliance to hold it in place. This necessitated a change in the flywheel/flexplate bolt pattern, as well as the need for an externally balanced flexplate/flywheel.

[] 1986 Aluminum Cylinder heads were introduced in mid year on the L98 Corvette engines.

[] 1987

(A) Hydraulic Roller camshafts were introduced on production engines. The lifter bosses were increased in height to accept roller lifters.

(B) The alloy heads for use in the Corvette still retain the non-angled bolts (center 2 bolts attaching to the intake).

(C) The valve cover surfaces were changed such that cylinder head mounting lip was raised and the bolt location was moved from 4 bolts on the perimeter, to 4 bolts down the centerline of the valve cover. This design debuted on the 1986 Corvette.

(D) The mounting angles of the center 2 bolts on each side of the intake manifold was changed from 90 degrees to 73 degrees.

(E) All carburetors were done away with and replaced by TBI (throttle-body injection) fuel injection on the Camaro and Firebird.

[] 1996 This was the last change for the Generation I engine, and continued through the end of the production run in 2003. All 1997 - 2003 Generation I engines were Vortec truck engines. The cylinder heads were redesigned using improved ports and combustion chambers similar to those in the Generation II LT1, resulting in significant power increases. The intake manifold bolt pattern was also changed to four bolts per cylinder head instead of the traditional six.

 

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