Heads are large metal components which are bolted to the engine block and form the top of the combustion chamber. On most1 modern engines, the valves are contained within them, and some heads house the camshaft(s). Between the engine block and the head is a head gasket which forms a seal between the two parts.
A Cylinder Head Being CNC Machined
This is a billet cylinder head being CNC machined for a high performance Duramax application. This YouTube video hosted by CentroidCNC.
- Side-valve engines have valves based in the block, to the side of the piston. These "flat head" designs have no valves in the cylinder head, which just serves as a cap for the top of the combustion chamber. This engine design fell out of favor in the late 1950s and the last mass-produced engine was seen in the early 1960s.