The valve spring exerts stress against the valve retainer to maintain the valve closed. When the rocker arm in a pushrod engine, or the cam follower in an engine moves and pushes the valve open, the strain exerted from the spring increases.
A valve spring is placed around the stem of a valve and held in place by a retainer. Its main job is to control the entire valvetrain, ensuring that the proper amount of spring pressure is applied consistently to prevent valve bounce.
Since valve bounce can lead to complete engine failure, power loss, and even breakage within the valve, these springs have quite an important job.
Additionally, a valve spring also helps to prevent valve float, or a disconnect between the camshaft lobe and the valvetrain that happens when the engine’s speed has outpaced the valve springs.
The springs help to protect the axle, cylinder walls, pistons, and the bearings of the engine because they force the valves to completely close, securing the proper amount of compression.