Britannica Sources used in this answer

What parts are usually located in the cylinder head of a gasoline engine?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Labeled cross-sectional diagram of a V-type gasoline engine for an automobile, showing internal components such as pistons, crankshaft, camshaft, intake and exhaust valves, connecting rods, spark plugs, and intake manifold. — gasoline engine Cross section of a V-type engine.

In a gasoline engine, the cylinder head serves as a critical component that seals the top of the cylinder to form the combustion chamber. The parts typically located in or mounted on the cylinder head include:12

Valves: These include the intake and exhaust valves, which control the flow of the air-fuel mixture and exhaust gases. In overhead-valve (OHV) and overhead-cam (OHC) engines, these valves are housed entirely within the cylinder head.132
Spark Plugs: The cylinder head contains threaded holes to accommodate spark plugs, which are essential for igniting the air-fuel mixture.142
Valve Train Components: Depending on the engine design, the cylinder head may carry valve seats, valve guides, and valve ports. In many configurations, it also houses rocker arms, which transmit motion to the valves.153
Camshafts: In overhead camshaft (OHC) or dual overhead camshaft (DOHC) engines, the camshaft itself is located directly in the cylinder head above the valves.13

The specific configuration of these parts depends on whether the engine uses an overhead-valve design or an older L-head design, where some components were housed in the cylinder block.1