An internal combustion engine's cylinder head performs several functions including housing the exhaust and intake valves, the fuel injector and necessary linkages, and passages for the fuel and air mixture. In water-cooled engines, the cylinder head also contains integral ducts and passages for the engine's coolant to facilitate the transfer of excess heat away from the head and, therefore, the engine in general.
Cylinder heads are made up of many channels or passageways. They are used as conduits for air and fuel to reach the engine's combustion chamber. Exhaust fumes exit the engine via the channels in the cylinder head.