It was 1955 when Ed Cole’s Chevrolet engineering group got together to build a more powerful engine for the new Corvette. At the time, the Corvette’s engine was a 165 horsepower six cylinder. The replacement dreamed up and built by Ed Cole and his team, was an all-new small block V8 with 265 cubic inches that went from a drawing to production in just 15 weeks. This very first overhead valve small-block V8 didn’t even have a provision for an oil filter. A new block casting was developed in 1956 that incorporates the oil filter boss on the engine.
There was a new engine debut in 1957, as the introduction of the 283ci engine marked the end of the 265ci engine. Chevrolet also developed a new engine mounting system by relocating the engine-mounting location from the front of the block, to placing the mounts near the freeze plugs on the side of the block.
Before 1963, all small-block Chevy engines used a Road Draft Tube to ventilate the crankcase. To make this work, there was a large hole at the top rear of the engine block inside the lifter valley that led to a breather tube at the rear of the engine. In 1963, In 1969, the PCV system was incorporated. The vent hole and the oil fill tube at the front of the intake was also gone.
In 1962, the new Chevy II had shock towers that were in the engine bay. This put the steering components where the oil pan would be. To solve this problem in V8 applications, a special engine block was designed. The block featured a recessed oil filter boss, and a dipstick located on the passenger’s side. The clearance problem was eliminated with the 1968 redesign of the Nova, but the unique 1964-1967 blocks are still highly collectible.
Several other changes came about in 1967. This was the last year of the 283ci engine, and the first year of the 350ci engine. It was also the first of a three year run for the 302ci Chevy.
In 1968, Chevrolet started making the small blocks with large journal crankshafts, greatly improving strength and durability. This year also marked the first year of the 307ci engine. The 307ci engine has the stroke of a 327ci engine and the bore of a 283ci engine.
The introduction of 1969 brought us four-bolt main bearing caps, but also marked the last year of the 327ci engine, and the 302ci engine.
In 1970, the gen-one small block grew to its largest factory displacement of 400 cubic inches. These blocks utilized Siamese-bore cylinders to make room for the large displacement. There were also steam holes drilled into the surface of each deck to promote cooling. These steam holes require the use of 400-specific cylinder heads.
In 1976, an engine was designed to combat the gas embargo, CAFE mandates, and tighter emissions standards. The 305ci engine became Chevrolet’s cost-effective, all-purpose economy V8. During the early 1980s, when Chevrolet was streamlining their engine lineup, the 305ci engine became the “Corporate” V8 engine, (many times the only V8), in many GM vehicles.
In 1980, the small block received a change that placed the oil dipstick on the passenger’s side of the block. There seems to be no clear cut reason for the change. Another year of change was 1986.This is when the two piece rear main seal was replaced with a one piece unit. Displacement of the block was also cast into the block next to the casting number.
To say that Chevrolet’s small-block V8 changed the face of automotive engine history is an understatement. When it debuted in 1955, who knew how much of an influence it would have for the next 60 years.