The Chevrolet small-block engine is a series of gasoline-powered V8 automobile engines, produced by the Chevrolet division of General Motors in two overlapping generations 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 to in displacement, until the advent of the LS7 in the 2006 Corvette C6 Z06. 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.

The Generation II small-block engine, introduced in 1992 as the LT1 and produced through 1997, is largely an improved version of the Generation I, having many interchangeable parts and dimensions. Later generation GM engines, which began with the Generation III LS1 in 1997, have only the rod bearings, transmission-to-block bolt pattern and bore spacing in common with the Generation I Chevrolet and Generation II GM engines.

Production of the original small-block began in late 1954 for the 1955 model year, with a displacement of , growing over time to by 1970. Among the intermediate displacements were the , , and numerous 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 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. Chevrolet also produced a big-block V8 starting in 1958 and still in production as of 2024.

Finally superseded by the GM Generation III LS in 1997 and discontinued in 2003, the engine is still made by a General Motors subsidiary in Springfield, Missouri, as a crate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 between 1955 and 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 The Highest Mileage Chevrolet In The World, hotcars.com, January 14, 2025 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.

Overview The first generation of Chevrolet small-blocks began with the 1955 Chevrolet 265 cu in (4.3 L) V8 offered in the Corvette and Bel Air. The engine quickly gained popularity among stock car racers, and was nicknamed the "Mighty Mouse," after the then-popular cartoon character, later abbreviated to "Mouse". By 1957 the engine had grown to . Fitted with the optional Rochester mechanical fuel injection (FI) and a Duntov high-lift camshaft, it was one of the first production engines to produce per . The 283 was adopted by other Chevrolet models, replacing the 265 V8s.

A high-performance variant followed, turning out as much as (SAE gross power, not SAE net power or the current SAE certified power values) and raising horsepower per cubic inch to . From 1954 to 1974, the small-block engine was known as the "Turbo-Fire" or "High Torque" V8. However, it was the series that became the best-known Chevrolet small-block.

Installed in everything from station wagons and sports cars to commercial vehicles, boats, industrial equipment, and even (in highly modified form) in aircraft, the 350 is the most widely used small-block engine of all time. Though not offered in GM vehicles since 2003, the 350 series is still in production at a GM subsidiary in Springfield, Missouri, under the company's "GM Genuine Parts" brand, and is also manufactured as an industrial and marine engine by GM Powertrain under the "Vortec" name.

3.750 in. bore family (1955–1957) 265

The "Turbo-Fire" V8 was the second Chevrolet small-block; the first Chevrolet V8 was produced in 1917. The 265 cu in Turbo Fire engine was designed by Ed Cole's group at Chevrolet to provide a more powerful engine for the 1955 Corvette than the model's original "Blue Flame" in-line six; the 2-barrel debut version went from drawings to production in just 15 weeks.

Cole's design borrowed a stud-mounted independent ball rocker arm valvetrain design patented by Pontiac engineer Clayton Leach scheduled to be used in the 1955 Pontiac V8. Internal GM rules at the time held that an automotive division developing a technological innovation had the right to introduce it and enjoy a two-year hiatus before any other GM division could share it. GM overruled itself and both divisions debuted the new design. This provided a considerable advantage to Chevrolet, as the Pontiac V8's introduction had been held back: it had been tracking for introduction in the 1953 model year, and all 1953 and 1954 Pontiac cars' chassis and suspensions had been designed for the new engine. But GM's Buick division had successfully lobbied corporate management to postpone Pontiac's engine until late 1954 in favor of Buick's release of its new overhead valve (OHV) V8 engine in 1953.

An OHV engine with hydraulic lifters, the small-block was available with an optional four-barrel Rochester carburetor, increasing engine output to , or in the Corvette. The short-stroke bore × stroke engine's bore spacing would continue in use for decades.

Also available in the Bel Air sedan, the basic passenger car version produced with a two-barrel carburetor. Upgraded to a four-barrel Rochester, dual exhaust "Power Pack" version, the engine was conservatively rated at , and with the "Super Power Pack," it was boosted up to the power level of the Corvette.

A shortcoming of the 1955 265 was its lack of any provision for oil filtration built into the block, instead relying on an add-on filter mounted on the thermostat housing, and that was an "option only." In spite of its novel green sand foundry construction, the lack of adequate oil filtration leaves it typically only desirable to period collectors.

The 1956 Corvette introduced three versions of this engine— with a single 4-barrel carburetor, with twin 4-barrels, and with two four-barrel carburetors and a high-lift camshaft.

Year Power Output Torque Output Fuel System Compression Ratio Notes 1955 @ 4,000 rpm @ 2,000 rpm 2-barrel 7.5:1 @ 4,400 rpm @ 2,200 rpm 8.0:1 @ 4,600 rpm @ 2,600 rpm 4-barrel @ 5,000 rpm @ 3,000 rpm 1956 @ 4,200 rpm @ 2,200 rpm 2-barrel 7.5:1 @ 4,400 rpm @ 2,200 rpm 8.0:1 @ 4,400 rpm @ 2,400 rpm @ 4,600 rpm @ 3,000 rpm 4-barrel 9.25:1 @ 5,200 rpm @ 3,200 rpm @ 5,200 rpm @ 3,600 rpm 2x 4-barrel 1957 @ 4,200 rpm @ 2,400 rpm 2-barrel 8.0:1 @ 4,400 rpm @ 2,400 rpm

3.875 in. bore family (1957–1973) 283

The engine appeared in 1957, achieved by boring out the by , yielding a bore × stroke. The first 283 motors used the stock 265 blocks. However, the overbore resulted in thin cylinder walls, causing future 283 blocks to be cast to accept the larger bore. Multiple different versions between and were available, variously with a single carburetor, twin carburetor, or fuel injection. Horsepower was up a bit each year from 1958 to 1961. The 1957 Rochester Ramjet mechanical fuel injection version produced an even 1 hp per cu in (0.75 kW; 1.01 PS per 16.4 cc), an impressive feat at the time. This was the third U.S.-built production V8 to produce one horsepower per cubic inch, after the 1956 Chrysler 300B and DeSoto Adventurer.

The 283 engine was optional in Checker Taxis beginning in 1965.Flory, J. "Kelly", Jr. American Cars 1960–1972 (Jefferson, NC: McFarland & Coy, 2004), p.341. A GM Canada version was also available in Studebaker vehicles produced there for 1965 and 1966.

Year Power Output Torque Output Carburetor Notes 1957 @ 4,200 RPM @ 2,000 RPM 2-barrel @ 4,600 RPM @ 3,000 RPM 4-barrel @ 4,800 RPM Corvette @ 5,000 RPM @ 3,800 RPM 2x 4-barrel @ 5,000 RPM @ 3,800 RPM Fuel injection @ 6,000 RPM @ 4,200 RPM 2x 4-barrel Competition camshaft @ 6,200 RPM @ 4,400 RPM Fuel injection 1958 @ 4,200 RPM @ 2,000 RPM 2-barrel @ 4,400 RPM @ 2,400 RPM 4-barrel @ 4,600 RPM @ 2,400 RPM 2-barrel @ 4,800 RPM @ 3,000 RPM 4-barrel @ 5,000 RPM @ 3,800 RPM 2x 4-barrel @ 5,000 RPM @ 3,800 RPM Fuel injection @ 6,000 RPM @ 4,200 RPM 2x 4-barrel Competition camshaft @ 6,200 RPM @ 4,400 RPM Fuel injection 1959 @ 4,200 RPM @ 2,000 RPM 2-barrel @ 4,400 RPM @ 2,400 RPM 4-barrel @ 4,600 RPM 2-barrel @ 4,800 RPM @ 3,000 RPM 4-barrel @ 5,000 RPM @ 3,800 RPM 2x 4-barrel @ 5,000 RPM @ 3,800 RPM Fuel injection @ 6,000 RPM @ 4,200 RPM 2x 4-barrel Competition camshaft @ 6,200 RPM @ 4,400 RPM Fuel injection 1960 @ 4,200 RPM @ 2,000 RPM 2-barrel @ 4,200 RPM @ 2,200 RPM @ 4,800 RPM @ 3,000 RPM 4-barrel @ 5,000 RPM @ 3,800 RPM 2x 4-barrel @ 6,000 RPM @ 4,200 RPM Competition camshaft @ 5,200 RPM @ 4,400 RPM Fuel injection @ 6,200 RPM @ 4,700–5,100 RPM Competition camshaft 1961 @ 4,200 RPM @ 2,000 RPM 2-barrel @ 4,200 RPM @ 2,200 RPM @ 4,800 RPM @ 3,000 RPM 4-barrel @ 5,000 RPM @ 3,800 RPM 2x 4-barrel @ 6,000 RPM @ 4,200 RPM Competition camshaft @ 5,200 RPM @ 4,400 RPM Fuel injection @ 6,200 RPM @ 4,700–5,100 RPM Competition camshaft 1962 @ 4,200 RPM @ 2,000 RPM 2-barrel @ 4,200 RPM @ 2,200 RPM 1963 @ 4,400 RPM @ 2,400 RPM 2-barrel @ 4,800 RPM @ 2,400 RPM 1964 @ 4,400 RPM @ 2,400 RPM 2-barrel RPO L32 @ 4,800 RPM @ 2,400 RPM RPO L32 @ 4,800 RPM @ 3,200 RPM 4-barrel RPO L77 1965 @ 4,400 RPM @ 2,400 RPM 2-barrel RPO L32 @ 4,800 RPM @ 2,400 RPM 2-barrel @ 4,800 RPM @ 3,200 RPM 4-barrel RPO L77 1966 @ 4,400 RPM @ 2,400 RPM 2-barrel RPO L32 @ 4,800 RPM @ 2,400 RPM 2-barrel @ 4,800 RPM @ 3,200 RPM 4-barrel RPO L77 1967 @ 4,600 RPM @ 2,400 RPM 2-barrel Source: GM Vehicle Information Kits

307 An economy version was produced from 1968 through 1973 as Chevrolet adjusted to increasingly stringent federal emissions standards. Engine bore and stroke was .Chevrolet Motor Division - General Motors. Chevrolet Pickup Trucks Sales Brochure #4. Chevrolet Pickup Division - General Motors, Aug. 1967, xr793.com/wp-content/uploads/2020/12/1968-Chevrolet-Pickups.pdf. All 307s had two-barrel carburetors, and large journals to accept the 327's crankshaft. Pistons used with the 307 share the same pin height as the 327 but retain the 283's bore size.

1968–1971 Chevrolet Camaro 1968–1973 Chevrolet Chevelle 1968 Chevrolet Impala 1968–1973 Chevrolet Nova 1971–1972 Pontiac Ventura 1968–1972 Chevrolet C/K (second generation) 1973 Chevrolet C/K (third generation)

4.000 in bore family (1962–2002) Originally intended as the Chevrolet Division's performance block, the 4.000 in bore engine family was introduced in a displacement in the 1962 Corvette. This was followed by a de-stroked racing version introduced in the 1967 Chevrolet Camaro Z/28. The first displacement was the high-performance L-48 option for the 1967 Camaro. Many variants of 350 followed, at all levels of performance, turning it into an all-purpose engine that saw use in applications from Corvettes to trucks. All engines in this family share the same block dimensions and sometimes even the same casting number; the latter indicating engines were of the same block, but with different strokes (e.g., the casting number 3970010 was used by all three displacements).

The engine family received a increase in main journal size in 1968 to . The last variant a 2000s 350 used in pickup trucks and commercial vehicles.

The medium journal 350 was further developed into the Generation engine GM LT engine 350 in the early 1990s.

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