What is the bore and stroke (in inches) of the Chrysler 426 Hemi?

The Chrysler 426 Hemi had a 4.25-inch bore and a 3.75-inch stroke.

Those dimensions describe the diameter of each cylinder and the distance each piston traveled. With eight cylinders, they produced a calculated displacement of about 425.6 cubic inches, rounded and marketed as 426 cubic inches.

The engine was Chrysler’s second-generation Hemi, developed during the early 1960s for NASCAR and drag racing. Its hemispherical combustion chambers allowed large, well-angled valves, while the tall RB-series architecture provided room for the engine’s substantial displacement and strength-oriented components.

The 426 Hemi is commonly confused with Chrysler’s 426 Wedge because both engines shared the same bore and stroke. Their cylinder heads and combustion-chamber designs were different, however: the Hemi used hemispherical chambers, while the Wedge used a wedge-shaped design. The 4.25-by-3.75 specification applies to the famous 426 Hemi family.