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Engine and Engine Build Terminology

Engine Terminology​

Square Bore​

An engine configuration where the bore and stroke dimensions are identical, such as 54mm x 54mm.

Under Square​

An engine design characterized by a bore that is smaller than the stroke, for instance, 52.4mm x 57mm.

Over Square​

An engine type where the bore exceeds the stroke, exemplified by 51mm x 57mm.

Deck Height​

The measurement from the uppermost edge of the cylinder to the outermost edge of the piston crown when at top dead center.

Pin Height​

The distance from the center of the wrist pin to the uppermost edge of the piston crown or face.