CRANKCASE

The lower part of the engine that surrounds the crankshaft . It contains the crankshaft , piston cylinders , connecting rods and other moving parts of the engine. As well, in non-air-cooled engines, it has a number of internal passages for the coolant and oil transfer. In air-cooled engines, it has internal passages for oil transfer; but usually it has fins on the exterior to dissipate the heat. The crankcase is not to be confused with the pan which is a thin steel cover that is bolted to the bottom of the crankcase .