The Chevrolet small-block engine... a series of V8 Engines built by the Chevrolet Division of General Motors using the same basic small (for a V8) engine block.
Retroactively referred to as the "Generation I" small-block, it is distinct from subsequent "Generation II" LT and "Generation III" LS engines.
Production of the original small-block began in 1955 with a displacement of 265 cu in (4.3 L) growing incrementally over time until reaching 400 cu in (6.6 L) in 1970.
Several intermediate displacements appeared over the years, such as the 283 cu in (4.6 L) that was available with mechanical fiel injection, the 327 cu in (5.4 L) (5.3L), as well as the numerous 350 cu in (5.7 L) versions.
Introduced as a performance engine in 1967, the 350 went on to be employed in both high- and low-output variants across the entire Chevrolet product line.
Although all four of Chevrolet's siblings of the period (Buick, Cadillac, Oldsmobile, and Pontiac) designed their own V8s, it was the Chevrolet 350 cu in (5.7 L) small-block that became the GM corporate standard!
Over the years, every American General Motors division except Saturn used it and its descendants in their vehicles. Finally superseded by GM's Generation II LT and Generation III LS V8s in the 1990s and discontinued in 2003, the engine is still made by a GM subsidiary in Mexico as an aftermarket replacement.
In all, over 90,000,000 small-blocks have been built in carbureted and fuel injected forms since 1955.