: It provides a mounting point for fuel injectors (in diesel or direct-injection engines) and spark plugs (in petrol engines).

: It forms the "roof" of the cylinders, containing the extreme pressure generated during ignition.

: It houses the intake and exhaust valves that open and close to let fresh air in and spent gases out.

: It contains passages for coolant to flow through, absorbing heat to prevent the metal from warping or melting. Key Components Inside