Main Components of Cylinder Heads & Their Function

by Richard May
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New car petrol engines image by Christopher Dodge from

The cylinder head is located at the top of the engine block. Made from aluminum or iron, it seals the piston chambers, ensuring adequate pressure within them. The first engines using this technology, comparable with the modern engines used to power automobiles today, were patented in the early 1860s. Since this innovation overcame the problem of containing the controlled explosion of fuel within the engine block, the basic design of engines with cylinder block, pistons and cylinder head has barely changed as of 2010.

Head Gasket

The head gasket, usually made from a thin piece of steel, seals the joint between the engine block and the cylinder head. Without the gasket the seal between them, the two components would fail, causing a loss of pressure that would in turn reduce the power output of the engine. Water could also enter the cylinder chamber and mix with engine oil, causing overheating and damage to the internal components.


Your car runs on the ignition of a mixture of fuel and air. Channels within the cylinder head allow gas left over from this ignition to flow away from the engine and into the exhaust system via the exhaust manifold. This channeling removes heat from the engine and prevents the internal pressure from rising too high and causing an explosion.


On overhead valve engines, the inlet valve assembly sits at the top of the piston chamber, within the cylinder head. The valves control the flow of fuel and air into the piston chamber before the spark plugs ignite them. In the place of these valves, fuel-injected engines have injection nozzles that force the fuel-air mixture into the cylinder chamber.

Spark Plug Mounts

Each cylinder requires an ignition source to ignite the fuel-air mixture. Spark plugs are fitted through threaded holes in the cylinder head with their electrodes inside the piston chamber. The threaded holes ensure a gas-tight seal, maintaining the pressure within the cylinder chamber.


Engines with an overhead camshaft have the camshaft assembly housed withing the cylinder head.The engine's crankshaft, located at the bottom of the engine block, drives the camshaft by means of a belt or chain. As it rotates, it opens the inlet valve of the next cylinder to fire.

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