Stroking Specs for a 400 SB Chevy


The 400-cubic-inch small-block Chevy engine (SBC) -- produced from 1970 through 1980 -- was Chevrolet's largest displacement small-block engine. Engine builders and enthusiasts have been swapping and interchanging SBC parts to come up with some interesting stroker combinations since then.

Factory 400 SBC Specifications

  • The production 400 displacement is achieved by using a block with a 4.125-inch cylinder diameter ("bore") and a crankshaft stroke of 3.75 inches. The piston is 4.125 inches in diameter, and it travels 3.75 inches from bottom to top.

Combinations Based on the 400 SBC Crankshaft

  • Early on, 400 crankshafts were commonly machined to reduce the main-bearing journal diameters (from 2.65 to 2.45 inches) to fit in the 350 block. With a cylinder "overbore" of 4.030 inches, the displacement increased to what is now the popular 383 stroker engine. Aftermarket cranks are now manufactured with the proper bearing journal diameters.

400 SBC Block Combinations

  • Another popular combination actually resulted in a "destroked" engine: installing the 350 crank in the 400 block results in a 377-ci engine. Bearing spacers are required for the 350 crank to fit in the larger main-bearing bores of the 400 block. Other popular 400-ci SBC-based stroker combinations include the 415/421-ci SBC (3.875-inch stroke) and 427/434-ci engines (4.00-inch stroke).


  • Using cranks with longer strokes typically requires machining for extra internal clearance. In some cases an aftermarket block may be required.

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