How to set valve clearances (tappets)

AINTAINING the correct valve or tappet clearance helps to keep the engine running efficiently, with less clatter, and increases the longevity of critical components. Valves are operated by lobes on the camshaft, which action the valve rocker arms, usually via push rods. As the camshaft raises one side of the rocker arm, the opposing side lowers, opening the valve by pushing down on the valve stem. Within that mechanism is a set amount of free play (or lash) – usually measured with the engine cold – between the rocker arm and the top of the valve stem. It’s designed to provide a working clearance while also accommodating the expansion caused when the engine reaches operating temperature.