What effect does excessive valve clearance have on valve operation?

Excessive valve clearance can significantly impact valve operation, specifically causing valves to open late and close early. When the clearance between the rocker arm and the valve stem is too great, it results in a delay in the opening of the valve due to the additional distance that must be covered before the rocker arm begins to push down on the valve. This delay leads to the valve failing to open at the precise time required for optimal engine performance, which is critical for maintaining proper timing in the combustion cycle.

Similarly, because the valve is not being fully pressed down for an adequate amount of time, the closure of the valve is also affected, causing it to close earlier than normal. This premature closure can lead to decreased engine efficiency, potential power loss, and interference with the exhaust and intake processes, adversely affecting overall engine performance.

Understanding this timing is crucial because any deviation, such as excess clearance, can disrupt the finely tuned balance required for optimal running conditions in reciprocating engines.