Definitions for "Rocker Arm"
Keywords:  camshaft, lever, pushrod, pivot, cam
A pivoted lever that transmits the action of the pushrod to the valve stem. (Pushrod upward action is converted to downward push on the valve stem. )
It is a pivoted lever which transmits the action of the pushrod to the valve stem.
The part you see under the valve cover. This part transmits the pushing force from the PRs to the valve stems by pivoting on a center shaft. Stock rocker arms have an output to input ratio of 1.1:1 but they can commonly be bought in the ratios 1.25:1, 1.4:1 for more valve lift without having to change the cam. Before using the high ratio rockers, check with your cams manufacturer to see if those rockers will work well with the cam.