The cylinder head bolts onto the top of the cylinder block where it forms the top of the combustion chamber.
In-line engines of light vehicles have just one cylinder head for all the cylinders. Larger in-line engines can have two or more.
V-type and horizontally-opposed engines have a separate cylinder head for each bank of cylinders.
Just as with engine blocks, cylinder heads can be made of cast iron, or aluminium alloy.
A head made of aluminium alloy is lighter than if it were made of cast iron. Aluminium also conducts heat away more quickly than iron. So with an aluminium-alloy head, the heat of combustion can be conducted away into the coolant more quickly.
Manufacturing the head is similar to manufacturing the block. A casting mold is made. Sand cores are put in to form any hollow areas. Depending on the engine, these can be for coolant and lubricant passages, and inlet and exhaust ports.
Air-cooled engines have cooling fins cast into the cylinder head. The underside of the head is shaped to form the combustion chamber.
Molten metal is poured in, and allowed to cool. The cores are broken out and removed, and the cylinder head cleaned of any sand. After casting comes machining. Surfaces that must seal are machined flat. Holes are drilled and tapped for attaching bolts and studs.
In sand-cast heads, the large holes that had contained sand are machined, then fitted with soft metal plugs, called core plugs.