In an Internal Combustion Engine, the top of the cylinder is covered by a separate cast piece known as the cylinder head. The cylinder head is bolted to the top of the cylinder block. It contains combustion chamber. Spark plug and sometimes valves are mounted in it. It incorporates passages for the flow of cooling water.

Cylinder head (Image credit: dodgeram.info)

The cylinder head is usually made of gray iron or aluminium alloy. Aluminium has the advantages of lightness in weight and high heat conductivity. It is cast separately from the cylinder block so that it may be removed for cleaning carbon and grinding valves. To retain compression in the cylinder, a flat piece of gasket is placed between the cylinder head and the cylinder block. In certain cases such as a racing car engine, a separate head is not used. But a single piece of cylinder block and a head is difficult and costlier to make, and the internal parts of the engine are not as accessible.

Following care should be taken when detachable heads are made:

A gasket is placed between the cylinder head and cylinder block to retain compression in the cylinder, to prevent leakage and to ensure metallic tight fir joint. The gasket should be able to withstand not only high pressure but also extreme temperature.

Following important gaskets are used in automobile engines:

1. Copper-Asbestos gasket.
2. Steel-Asbestos gasket
3. Steel-Asbestos-Copper gasket
4. Single steel ridged or corrugated gasket
5. Stainless steel gasket