What closes the valve in a cylinder head?

The spring plays a crucial role in closing the valve in a cylinder head. When the camshaft rotates, it pushes against the lifter, which in turn moves the rocker arm. As the rocker arm is actuated, it pushes the valve open, allowing air and fuel to enter the combustion chamber or exhaust gases to exit. Once the camshaft rotates past the point where it holds the valve open, the spring takes over and pulls the valve closed. This return action ensures that the valve seats properly, creating a tight seal.

The spring's tension is essential for the proper functioning of the engine, as it ensures that the valves close quickly and accurately, preventing any loss of compression or misfiring. A weak or broken spring can lead to poor engine performance and may even cause damage if the valve fails to close properly during operation. Therefore, the spring's function is integral to maintaining the timing and efficiency of the engine's valve cycle.