What is the bore stroke of a 350 small-block?
The standard bore is 4.000 inches and the stroke is 3.480 inches (101.6 mm bore and 88.4 mm stroke) for the classic Chevy small-block 350. This article explains these measurements, what they mean for displacement and performance, and notes important variations you may encounter in factory and aftermarket builds.
Key specifications for the standard 350 small-block
The following numbers define the typical Chevrolet 350’s bore and stroke.
- Bore: 4.000 in (101.6 mm)
- Stroke: 3.480 in (88.4 mm)
These dimensions yield a total displacement of about 349.8 cubic inches (roughly 5.73 liters) across eight cylinders, which is why the engine is commonly referred to as a 350 cubic inch V8. The bore and stroke also influence piston speed, torque characteristics, and how freely the engine can breathe at higher RPMs.
Context and variations
The Chevy small-block 350 has been a cornerstone of GM’s V8 lineup since its introduction in the late 1960s. For most stock rebuilds and factory specifications, the 4.000" bore and 3.480" stroke remained the standard across a broad range of model years and vehicles. However, variations exist in aftermarket and crate engine markets, where builders may modify bore or stroke to achieve different displacement targets while maintaining compatibility with the same basic block family.
As a practical note for enthusiasts, many performance paths involve one of two common directions: slight bore enlargement paired with a standard or modestly increased stroke (for torque and breathing) or a true stroker build that increases the crank throw (example: popular 383 cubic inch variant using a 4.030" bore with a 3.750" stroke). In all cases, it’s essential to verify that the chosen bore, stroke, pistons, rods, and machine clearances will fit the specific block and crank you’re using.
Why bore and stroke matter for the 350
The bore determines the cylinder diameter, affecting piston surface area, combustion chamber volume, and cooling requirements. The stroke sets the piston travel, influencing torque, engine width, and the RPM range where the engine makes peak power. The 4.000" x 3.480" combination is a balanced setup known for strong low- to mid-range torque and good reliability in a wide variety of applications, from hot rods to trucks.
Summary
In its stock form, the Chevy 350 small-block uses a 4.000-inch bore and a 3.480-inch stroke, yielding about 350 cubic inches of displacement. This pairing underpins the engine’s reputation for tractable torque and broad applicability, while aftermarket builders frequently explore bore and stroke variations to achieve higher displacement or different power characteristics. Always verify the exact specs on your particular block and crank when planning a build.
