my understanding of mechanical advance & vacuum advance, tell me i'm wrong

[vettestr]

Vector,
I read your method of finding/verifing amount of mechanical advance and I agree. If you set initial at 12 degrees and check total @ crankshaft at 3200 RPM (anything above 3k) to be sure all mechanical is in and find 22 degrees is max, you have 10 degrees mechanical.

Just a thought .... I bet the rotor was not sent to them with the distributor for repair ...so just as a sanity check make sure nothing is haging up on the rotor on the bottom side. I had this happen to me once so now I check when things are not as expected. Also in the mind fart catagory is the fact 20 degrees camshaft is 10 degrees crankshaft.

[Silverback51]

The vacuum advance should always be disconnected when you are setting your timing, otherwise it will affect the reading you are getting.


I also have to correct Jeff. 20 degrees of crankshaft rotation is 10 degrees of camshaft rotation. The crankshaft rotates twice (720 degrees) for every rotation (360 degrees) of the camshaft.