If the tappet clearance is increased, what effect does it have on the valves?

Increasing the tappet clearance leads to a situation where the valves are not held open as long during each cycle of the engine's operation. When tappet clearance is increased, the distance that the tappet must travel before it makes contact with the valve stem is also increased. As a result, the valve will close sooner than it normally would because there is a greater distance to traverse before reaching the point of valve lift.

This earlier closure can lead to decreased performance, as the valves will remain open for a shorter duration than intended. Consequently, less air and fuel may enter the combustion chamber, potentially affecting the engine's efficiency and power output. In contrast, having an appropriate tappet clearance ensures that the valves open and close at the optimal times for maximum engine performance.