The engine head is, by definition, the part of the internal combustion engine that is located on the block, above the cylinders. It closes the cylinders, thus forming the combustion chambers. Also, the engine head provides space for the passage of intake and exhaust ducts, and its role is also in housing valves, spark plugs, fuel injectors, camshaft bearings and other engine parts. Certainly, when we say that the engine head is located “above” the engine block, it is only a descriptive definition, the engine can be positioned in the vehicle so that the head actually comes from the side, at an angle, etc.
In-line engines, i.e. those in which the cylinders are placed in a line, usually have one head. Engines with a V-configuration cylinder arrangement usually have two cylinder heads, one for each row of cylinders. Finally, boxer engines with opposed cylinders have two heads. V engines with a small gap between the cylinders, such as Volkswagen’s VR6, use a single head. Finally, there are exceptions to this theory.
Let’s say, just for fun, that some large (mostly diesel) engines such as those that drive ships or are used in industrial plants can have one head for each cylinder. This construction is used to reduce costs and simplify possible repairs.
In today’s cars, there are almost no engines whose head is not made of some aluminum alloy, while blocks made of gray cast iron (cast iron) are still somewhat common.
The reason for this lies primarily in the fact that aluminum alloys can withstand thermal loads better (aluminum conducts heat much better than iron) to which the engine head is exposed because it gets extremely hot during operation.
Certainly, in the engine head there are chambers for combustion of the mixture, which is one of the fundamental reasons for the significant heating of this part of the engine.