The terms "big block" and "small block" became popular in the sixties when American manufacturers developed a second larger group of V8 pushrod engines, usually for trucks and NASCAR racing. An approximate dividing line seems to be whether the original engine is above or below 350 cubic inches.

Chevrolet motors were based on the 265/283/327 "small block" vs. 348/396/409 engine block. Ford sizes 292 and 260/289/305/351 "small block" vs. 427/428/429 "big block."