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Square Bore - An engine with the same bore x stroke , example 54mm x 54mm
Under Square - An engine with smaller bore than stroke , example 52.4mm x 57mm
Over Square - An engine with a larger bore than stroke , example 51mm x 57mm
Deck height - The distance from the top edge of the cylinder to the outer edge of the piston crown at top dead center.
Pin height - The distance from the center of the wrist pin to the upper edge of the piston crown or face.