A typical internal combustion engine consists of three major elements: the cylinders in which the pistons move; the cylinder head where the fuel/air combination enters, where combustion occurs, and where the burned gasses are vented off; and the crankcase which houses the crankshaft and usually the oil supply. The crankcase is usually the major part of the engine, and takes up most of the structural area of the engine, and therefore is much of what is referred to as the block.