What does the rocker arm in a car do?

In an internal combustion engine, the purpose of the rocker arm is to transfer motion from the camshaft to the valve. As the camshaft rotates, it lifts the rocker arm, which in turn opens the valve. The rocker arm is a pivotal lever, and its fulcrum is usually a fixed point on the cylinder head. The camshaft lobe pushes on one end of the rocker arm, while the valve stem is connected to the other end. When the camshaft lobe is not pushing on the rocker arm, the valve spring closes the valve.

Rocker arms are typically made of steel, aluminum, or cast iron. They are designed to be strong enough to withstand the forces that are applied to them, and they must also be lightweight to reduce the overall weight of the engine.

The rocker arm ratio is the ratio of the distance from the camshaft lobe to the fulcrum of the rocker arm, to the distance from the fulcrum to the valve stem. The rocker arm ratio affects the amount of lift that the valve receives. A higher rocker arm ratio produces more valve lift, but it also puts more stress on the rocker arm and the valvetrain.

Rocker arms are an essential part of the internal combustion engine, and they play a critical role in controlling the flow of air and fuel into and out of the engine.