What is a quick method to check if valve timing has jumped?

To determine if valve timing has jumped, checking valve movement at TDC (Top Dead Center) on the exhaust stroke is effective. When the engine is at TDC on the exhaust stroke, the exhaust valves should be closing, and the intake valves should be fully closed. If valve timing is off, you may observe unusual positions of the valves compared to expected behavior. This could indicate that the timing mechanism has slipped, causing a misalignment in the engine’s timing.

In engines, each stroke has specific expectations regarding the timing of the valve openings and closings. Checking at TDC on the compression stroke focuses on the position of the intake valves and other dynamics relevant to combustion. However, the exhaust stroke is crucial for assessing if the timing has jumped because it directly relates to when valves should be closing. If timing has indeed been interrupted, the exhaust valves may not be in their appropriate position at this point in the cycle.

Other methods, like looking at timing mark alignment or checking timing chain or belt slack, can also provide insights but might not offer a quick visual confirmation of whether timing has truly jumped. A misalignment might not be as evident without further disassembly.