Cylinder head

A cylinder head is a component attached to the cylinder block through the head gasket using nuts or bolts that, together with the cylinder and the piston, forms the combustion chamber.
Since it is subject to high temperatures and high pressures while the engine is running, in water-cooled engines, it is typically made of cast iron and provided with a water jacket that allows cooling water to pass through internally.
In air-cooled engines, it is typically made of an aluminum alloy and, at the same time, provided with integrally cast fins to improve cooling effects.
Furthermore, cylinder head structures are different for gasoline engines and diesel engines, and differ based on cooling method, combustion method, and valve arrangement, etc.
For example, overhead valve (OHV) air-cooled gasoline engines have recesses on the lower surface of the cylinder that form combustion chambers into which valve mechanisms such as inlet valves and exhaust valves, as well as ignition plugs, etc. are incorporated.
The lower surfaces of cylinder heads on diesel engines are almost flat in order to increase compression ratios and provide good combustion, and in addition to incorporating the likes of valve mechanisms (such as intake valves and exhaust valves), injection nozzles, and glow plugs (that, when energized, glow red to improve cold startability), pre-chamber types are provided with mechanisms such as swirl chambers.

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