The engine is the cylinder block and cylinder head made of two parts, connected to each other by a bolt.

Block material should have sufficient strength, good casting properties and machinability, and the price is lower, so the common block material is cast iron, alloy cast iron. However, the more common aluminum alloy cylinder block, the cylinder because light weight aluminum, an excellent thermal conductivity, the capacity of the coolant can be reduced. After the start, the cylinder quickly reaches operating temperature, and the coefficient of thermal expansion of aluminum pistons and exactly the same, a small gap variation after heating, to reduce the impact of noise and oil consumption. And aluminum cylinder heads and thermal expansion of the same work to reduce thermal shock generated by the thermal stress.