Curved levers which transfer a ‘push’ from a push rod to a valve stem inside the top of the engine in order to make the valves open. The valves are what let air in and exhaust out of the cylinder.
Older engines are called Overhead Valve (OHV) engines and use pushrods to move the rocker arms up and down. New engines are called Overhead Cam (OHC) engines and the cam shaft lobes directly connect to the rocker arms to move the valves.
You may have heard people with an engine noise called tapping, or top end noise. This is usually caused by either a rocker arm worn out, loose or a related part in the rocker arm / valve system. It is referred to as top end noise, because the rockers and valves are on top of the engine, as opposed to a bottom end noise, which is usually a knock caused by lower engine bearings.
Leave comments below or see these