A rocker arm is an oscillating lever that conveys radial movement from the camshaft lobe into linear movement at the poppet valve. In a pushrod engine, the pushrod pushes up on one side of the arm, causing it to pivot on its trunnion and press down on the valve stem to open it. High-performance builds often upgrade to roller rocker arms to reduce friction and handle higher valve spring pressures.
You can hear a distinct ticking from the top end, which usually means a loose rocker arm needs a lash adjustment.
Also heard as
- rocker
Related terms
Pushrod
A metal rod that transfers motion from the camshaft to the rocker arms in overhead valve engines.
Tappet
A mechanical component that transfers linear motion from a camshaft lobe to a valve stem or pushrod.
Overhead valve
An engine design where the intake and exhaust valves sit in the cylinder head above the combustion chamber.
Overhead cam
A valvetrain layout where the camshaft is located in the cylinder head above the combustion chamber.
Cylinder head
This cast metal component bolts to the top of the engine block to seal the combustion chambers.