Re: Can Someone Good With Vacuum Gauge Help Me Diagnose Engine Trouble???

Posted by Ross On 2015/8/24 5:56:53

With the timing that far advanced I would expect the engine to be quite "skippy", as it seems that it is.


The goal is not to get the maximum idle vacuum. The advance curves are calibrated to the combustion characteristics at many speeds and loads. At 11 or 15 degrees the car will not drive well, and will certainly not give maximum power as the cylinder pressure will peak well before the piston reaches top dead center. Even so, it might not ping, depending on the compression ratio. Also, the car will uncommonly hard to start when it is hot.


I would not be remotely concerned that the idle vacuum reading is a a bit low at this stage in the engine's life. It often takes quite a while for these engines to break in; until they do you have extra blow-by past the rings, and the extra friction will will take several points off the idle vacuum reading.

Just set the timing to 6 or 7 at a low idle and go for a long drive.