FAA Powerplant Written Practice Test 2026 – Complete Exam Prep

Excessive valve clearance results in a decrease in valve opening duration for both the intake and exhaust valves. This phenomenon occurs because when the clearance is too large, the valve will close sooner after the camshaft has actuated it. As a result, the valve does not remain open as long as it should, leading to reduced effective opening durations.

In engines, proper valve clearance is critical for ensuring that the valves open and close at the correct times as dictated by the camshaft profile. When the clearance is excessive, it can also negatively affect engine performance, as the engine may not receive the adequate amount of air and exhaust gases during the induction and exhaust strokes. Therefore, maintaining proper valve clearance is essential for optimal engine operation and efficiency.

Understanding the relationship between valve clearance and opening duration is vital for diagnosing engine performance issues and ensuring that the engine runs smoothly and efficiently.