Re: Engine Timing

Posted by Ross On 2020/3/29 7:01:54

I think this might pertain to the original question, but I have gotten lost.

Here is an easy method for a check on your vac advance. Hook up your timing light and start the engine. As you give gas to oh, 2000 rpm or so you will see the timing marks march past the pointer. Now snap the throttle shut. If the vac advance is working, you will immediately lose more than half the advance as the carb shuts off the supply of vacuum. As the revs drop the other half will fall away as the centrifugal advance retracts to its beginning position.

Oh, and to clear a point, the vac advance retards the timing as the engine is placed under load. At 50 mph on a flat road you will have full vac and centrifugal advance. Encounter a steep hill while maintaining 50 and the engine vac will drop as you open the throttle; the vac advance will relax its position and let the timing retard a bit to prevent pinging.