Re: 52' 300 timing / vacuum advance

Posted by Ross On 2024/5/22 6:24:35

You will need to set your base timing with the idle down in the 400-450 range. Otherwise, the centrifugal advance inside the distributor begins to kick in and you will get a false reading. I just had in a 52 with the idle set way high. When I got that cranked down it turned out the timing was about 8 degrees retarded which explained the overheating and poopy performance.

At low idle the carb is so constructed that the vac advance receives no vacuum and thus does nothing. I usually don't bother to disconnect them when checking timing --I just make certain the idle is good and slow--and there is no need at all to plug anything.

A short observation will show if everything is basically correct: while using your timing light slowly give gas. In very short order, the vac advance will kick in and the timing will jump. Give more gas and the timing will slowly increase with speed as the centrifugal advance does its job. Then snap the throttle shut and the timing will instantly jump way back as the vac advance goes out of the picture. Then as the engine slows to an idle the timing will return to base.