A rocker arm is a lever that conveys the motion of the camshaft to the valves of an internal combustion engine.
In the diagram the black part is the rocker arm. The blue part is the pushrod. The yellow part is the valve. The red part is the lifter also called a tappet. And the green part is the camshaft.
When the camshaft turns it lifts the lifter which pushes on the pushrod which rocks the rocker arm which presses down on the valve opening it. Then the air-fuel mixture can enter the cylinder and the process repeats.
There are typically two rocker arms per cylinder: one for the exhaust valve and one for the intake valve. The exhaust rocker arm is usually longer than the intake rocker arm because the exhaust valves are usually further away from the center of the cylinder than the intake valves are.
Rocker arms can be made out of several different materials including cast iron steel aluminum and even plastic. The reason for this is that rocker arms are subject to a lot of wear and tear and they need to be able to withstand a lot of heat and stress.
Rocker arms are usually mounted on shafts or pedestals that are located on the cylinder head. Adjusting the rocker arms is a way to adjust the valve clearance which is the distance between the valve and the rocker arm.
The rocker arm ratio is the ratio of the distance between the center of the pushrod contact point and the center of the rocker arm fulcrum to the distance between the center of the valve and the center of the rocker arm fulcrum.
A higher rocker arm ratio means that the valves will open further for a given lift of the cam. A higher rocker arm ratio also increases the valve spring load which can cause the valves to float at high RPMs.
Rocker arms are an important part of the valvetrain of an internal combustion engine and they play a crucial role in the engine’s performance.
Table of Contents
Is the rocker arm on a car a part of the engine?
No the rocker arm is not a part of the engine.
What is the rocker arm on a car?
The rocker arm is a part of the suspension system.