The term applied to valves which remain open after the piston has passed tdc or bdc at the end of a stroke in the four stroke cycle.

The term applied to valves which open before the piston has passed tdc or bdc at the beginning of a stroke in the four stroke cycle.

Cam follower or tappet.

The thickness of the valve head between the valve face and the head surface.

The control pin in, for example, a fuel injector. The needle works against an accurately shaped component to control flow.

The term used to describe the angle of crankshaft rotation when the inlet and exhaust valves are both open.

The bevelled surface annular face in the cylinder head that closes each port and into which a valve seats and seals the port.

A steel insert fitted in aluminium and some iron cylinder heads to form a durable seating for the inlet and exhaust valves.

The spring that closes and holds closed the valve. It fits around the valve stem above the guide and between the cylinder head and valve spring retainer.

The shaft of a valve.