What Is a 350 Small Block? | Chevy’s Legendary V8

The 350 small block is Chevrolet’s 350-cubic-inch (5.7L) pushrod V8 engine, produced from 1967 through the early 2000s.

When someone says “350 small block,” they almost always mean the Chevrolet 350-cubic-inch Gen I small-block V8 — the engine that powered countless Camaros, Corvettes, C10 pickups, and later Vortec trucks. It earned its reputation as a durable, inexpensive, and endlessly rebuildable workhorse. The key thing to understand is that this isn’t a single engine but an entire family of engines that shares the same fundamental architecture.

Defining The 350 Small Block

The Chevrolet 350 small block is a 90-degree V8 with pushrod-operated overhead valves and 16 valves total. Its bore and stroke measure 4.000 inches by 3.480 inches, which gives it the displacement of 350 cubic inches (5.7 liters). The engine block itself is cast iron, while cylinder heads vary between cast iron and aluminum depending on the version and year.

This engine family has a bore spacing of 4.40 inches across the cylinder centers, a dimension that stayed consistent through the Gen I production run. The standard firing order is 1-8-4-3-6-5-7-2, which remains the same across nearly all Gen I small-blocks.

The History Of The 350

Chevrolet produced small-block engines in overlapping generations from 1954 to 2003. The 350 debuted in 1967, introduced as a larger-displacement option within the same Gen I family that began with the 265 in 1954. It quickly became the corporate-standard small-block size across General Motors, appearing in passenger cars, trucks, and marine applications.

In GM truck use, 350-based Vortec versions ran from 1997 to 2003, and these are some of the most sought-after engines in the used market thanks to their improved cylinder heads and higher output. It’s important to distinguish these from the Gen II LT1 that appeared in 1992 — that engine used a reverse-flow cooling system and a distributorless ignition, making it a separate design from the classic Gen I 350 family.

350 Small Block Specs And Ratings

Horsepower figures for the 350 small block vary enormously by era, application, and rating method. Gross ratings from the late 1960s and early 1970s are not directly comparable to the net ratings used after 1972, so comparing a 1969 “350 horsepower” 350 to a 1980s “190 horsepower” truck engine requires context.

Chevrolet Performance still sells 350-cubic-inch crate engines today, and the Chevrolet Performance 350 crate engine page lists current offerings including an SP350/385 rated at 385 horsepower at 5,800 rpm and a 420-horsepower version. These modern crate engines use the same basic architecture as the classic 350 but with updated components like aluminum heads and more aggressive camshafts.

One common mistake is assuming every 350 shares the same rear main seal design. Pre-1986 Gen I engines use a 2-piece rear main seal, while 1986 and later versions use a 1-piece seal. They aren’t interchangeable without machine work, which is why knowing your engine’s year matters before ordering parts. If you’re planning a build or rebuild, your cylinder head choice is the biggest performance decision you’ll make — you can compare tested options in our roundup of the best 350 small block heads to see what fits your budget and goal.

Identifying Your 350 Small Block

The “350 small block” label doesn’t tell you everything about a specific engine. Compression ratios, power ratings, cylinder heads, fuel systems, and production years all differ across the family. A 1969 350 from a Camaro uses a different intake, camshaft, and cylinder head design than a 1998 Vortec 350 from a pickup, and neither is the same as an LT1 from the second generation that followed.

To identify what you have, check the casting numbers on the block and heads, then match them against production records. MotorTrend’s overview of the 350 small block walks through how these engines evolved from 1967 through the end of Gen I production, including which components changed over time. The casting number alone usually narrows your engine to a specific year range and application.

Remember that later LS-based engines — the 5.3L, 5.7L LS1, and others — share the “small-block” nickname but use a completely different architecture. They may be more powerful and efficient, but they aren’t the same engine family and parts don’t interchange.

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