Engine valves are mechanically opened and closed, to admit air or expel exhaust gasses, into the engine cylinder(s); the valves are located in the head casting of the engine.
The piston’s function is to act as a moveable plug in the cylinder, forming the bottom part of the combustion chamber.
Timing belts allow your vehicle’s engine to operate. They are in charge of synchronizing the rotation system of the engine’s camshaft and crankshaft, in order to enable engine valves to open and close at the right time.