Chevrolet 1955 – 1998 Small Block number-3
There are three engines in this family; the 302, the 327, and the 350. The first introduction, a 302, was meant to be high performance but the when the evolved version, a 350, later came into production it became an all use engine for Corvette sports cars, family sedans, and delivery vans. Every engine in this family have the same sized block casting with the same bore size and many even share the same casting numbers which confirms the stroke length determines the displacement of the engine. The 1968 model year sees the journal (refers to bearing type/size} modified to a medium sized 2.45 inch one. The original 1962 engine in this family is the small journal 327 and the end of the line with a medium journal 350 in 1992 for the last six years of production. This 350 would evolve into the “Generation II” LT ¼ 350 by the mid ‘90’s.
The 4.0 inch Bore Family 1962 to 1998
In 1966, specifically to meet the needs of the SCCA (Sports Club of America), a special 302 (4.9 L) V8 engine was produced for the Z/28 Camaro. This engine has the same 3 inch stroke as the 283 but is placed into a 327 cast iron block. This version was called a 5 liter and conforms to the Am Series road racing rules for the ’67 to ’69 seasons. For the ’67 model year the 302 uses a nodular cast crank as does the 283 but a forged steel crankshaft is also produced. In 1968 three engine blocks, the 302, the 327, and the 350 have the crank bearing revision with the new increase in rod journal size to 2.10 inches while the main bearings journal size is increased from 2.3 inches to 2.45. The new connecting rods are heavier so a larger, 3/8 inch cap bolt, is also used. For ’68 the blocks are produced in both a three and a four bolt design- the four bolts center has three main caps fastened with two added bolts and supported by thicker crack web bulkheads. With the increase in the journal to a standard size the steel used for the crankshaft is of higher quality as are the connecting rods and a high RPM eight inch harmonic balancer added. A second ¾ length tray is also added inside the oil pan called a windage tray to help keep the oil on vital parts at high RPM. The oil tends to splatter into droplets at higher RPM. For ’69 the pistons are upgraded to forged aluminum and have better sealing single-moly rings. The ’30-30 Duntov solid lifter cam used, 327 high performance heads are bolted on, special better sealing edge orifice lifters used which are motivated by the high performance Zora Arkus-Duntov camshaft-known as the “father of the Corvette”. The same Duntov cam is used from ’64-’67 carbureted 327/365 engines including the F.I. 327/375 power plants. The Duntov cam valves have a ‘202’ 2.02/1.60 diameter in the 327 “double-hump ;461 heads”, push-rod guide plates, the blue stripe pushrods, stiff valve springs, while the edge orifice lifters used ensure adequate valve train oil is in the crank case at high RPM. Continued…