Join Date: Aug 2009
Location: Madison, Alabama
You are correct about one thing; 302 is a Ford Motor, but it is Also a Chevrolet Motor as well. In 1967, Chevrolet was busy promoting their new pony car, the Camaro, and part of the promotional efforts included racing the Camaro in the SCCA Trans-Am series. In order to make the Camaro competitive, Chevrolet introduced the Z/28 option package which included among other things, a special 302 cubic inch small block. The engine size was a result of the SCCA's 305 cubic inch displacement limit in the Trans-Am series at the time. The 302 turned out to be one of Chevrolet's finest small block offerings, and the engine stood in stark contrast to the ever increasing size of the big blocks used in the muscle cars of the day.
To arrive at the SCCA legal 302 cubic inches, Chevrolet used a 4.00" bore and a 3.00" stroke resulting in a very oversquare (the bore is larger than the stroke) combination. In overly simple terms and ignoring such important design factors such as bore / stroke ratio, an engine with a short stroke has the ability to rev higher due to slower piston speeds. As an example, think of two engines, A and R. Engine A has a stroke of 3.00", while engine B has a stroke of 4.00". If both engines are turning at a speed of 4000 rpm, the pistons of engine A have less distance to travel than those of engine B. Since both engines are turning at the same rpm, the pistons of engine R have to cover more distance in the same amount of time as the pistons of engine A, resulting in higher piston speeds. Short stroke engines, therefore, can run higher rpm with greater reliability and less stress on the reciprocating assembly. This is the approach Chevrolet took when designing the 302 for SCCA competition.
The blocks used in 1967 were casting number 3892657. These small journal blocks were also used for 327 and 350 cubic inch engines as well (all three engines used a 4.00" bore). 1968 models used block casting number 3914678 and featured the new style large journals. The 1968 block was also used for the 327/210 hp and 350 295 hp SS engines. The blocks used in 1969 featured thicker webbing around the mains and used nodular iron 4 bolt caps. A common misconception is that 1967 and 1968 302's were 4 bolt blocks, while actually the only engine to use 4 bolt main caps was the 1969 version.