The appearance of an engine head varies according to the type of engine, whether it is an overhead valve engine, an overhead camshaft engine, a V-type engine or a horizontally-opposed engine. Regardless of the type of engine, the location of the engine head is always the same, being identified as the slab of cast iron or aluminum that caps off an engine block and turns the cylinders into sealed combustion chambers.
In some engines, such as an overhead valve type, the engine head can be basic in design and meant only to cover the engine block. In others, such as an overhead camshaft or a horizontally-opposed engine, the engine head can contain complex moving parts such as a camshaft, rocker arms, spark plugs and intake and exhaust valves.
V-type engines and horizontally-opposed engines generally contain two engine heads. The difference is that while the engine heads on a V6 or V8 engine are mounted in a way that forms the letter "V," those of a horizontally-opposed engine are aligned on the same horizontal plane.
Cast iron engine heads are cheaper and easier to produce than aluminum heads, but they are also heavier. In contrast, aluminum heads are lighter and dissipate heat better, but they are also more expensive to make. Most modern engine heads are made of aluminum.