Chevrolet small-block engine (first- and second-generation)

The Chevrolet small-block engine is a series of gasoline-powered V8 automobile engines, produced by the Chevrolet division of General Motors between 1954 and 2003, using the same basic engine block. Referred to as a "small-block" for its size relative to the physically much larger Chevrolet big-block engines, the small block family spanned from 262 cu in (4.3 L) to 400 cu in (6.6 L) in displacement. Engineer Ed Cole is credited with leading the design for this engine. The engine block and cylinder heads were cast at Saginaw Metal Casting Operations in Saginaw, Michigan.

Generation I and Generation II LT engines are distinct from subsequent LS-based small-block engines. The Generation II engine is largely an improved version of the Generation I, having many interchangeable parts and dimensions. Later generation engines have only the rod bearings, transmission-to-block bolt pattern and bore spacing in common with the Generation I and II engines.

Production of the original small-block began in late 1954 for the 1955 model year, with a displacement of 265 cu in (4.3 L), growing over time to 400 cu in (6.6 L) by 1970. Among the intermediate displacements were the 283 cu in (4.6 L), 327 cu in (5.4 L), and 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 of Chevrolet's siblings of the period (Buick, Cadillac, Oldsmobile, Pontiac, and Holden) designed their own V8s, it was the Chevrolet 305 and 350 cu in (5.0 and 5.7 L) small-block that became the GM corporate standard. Over the years, every GM division in America, except Saturn and Geo, used it and its descendants in their vehicles.

Finally superseded by the Generation III LS in 1997 and discontinued in 2003, the engine is still made by a GM subsidiary in Springfield, MO as a crate engine for replacement and hot rodding purposes. In all, over 100,000,000 small-blocks had been built in carbureted and fuel injected forms since 1955 as of November 29, 2011. The small-block family line was honored as one of the 10 Best Engines of the 20th Century by automotive magazine Ward's AutoWorld.

In February 2008, a Wisconsin businessman reported that his 1991 Chevrolet C1500 pickup had logged over one million miles without any major repairs to its small-block V8 engine.

All first- and second-generation Chevrolet small-block V8 engines share the same firing order of 1-8-4-3-6-5-7-2.