In a piston engine, the cylinder head sits above the cylinders, forming the roof of the combustion chamber. In sidevalve engines the head is a simple plate of metal containing the spark plugs and possibly heat dissaption fins. In more modern overhead valve and overhead camshaft engines, the head is a more complicated metal block that also contains the inlet and exhaust passages, and often coolant passages, Valvetrain components, and fuel injectors.
Side view of a DOHC cylinder head (with the valves and camshafts installed)
Underside of a OHV cylinder head (with the valves installed)
DOHC head- cutaway view
SOHC Honda D15A3 engine
A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process.
OHC engine combustion chamber, located between the piston (shown in yellow) and the valves (blue and red)
Dished piston for a diesel engine