Engine Block (Cylinder Block)

The engine block or cylinder block is the main structural part of an engine that contains the cylinders in which the pistons move. In cars, the block usually includes the crankcase as one big casting.

Motorcycle engines are built differently. Many singles and older twins have separate cylinders (barrels) bolted on top of a split crankcase. Many modern multi-cylinder engines have the cylinders cast together with the upper half of the crankcase, which saves weight and makes the engine stiffer, especially when it serves as part of the frame.

Cylinder bores often have a hard coating, such as nickel-silicon carbide, rather than a separate liner. Cracks in the block or crankcase, usually from a crash or a broken chain, can sometimes be welded by a specialist, but often mean replacement.