how to adjust vacuum advance

With an adjustable timing light yes you set your light to the total you want then zero the mark with the distributor. Remember you only want to consider your vacuum advance as part throttle cruise using ported vacuum. Setting your curve for a street car with vacuum advance is not as easy and the all in at 2000 ideas of old may not work in your environment, elevation and density altitude. I like weak but not flimsy springs that give you a smooth curve to about 3300 and find out just how much initial I can get away with on hot starts before shortening the advance slots under the breaker plate. Your desired cruise RPM plays a big role in how you set this up to achieve maximum mileage without detonation or "ping" and overheating issues. If you are running EGR you can get away with alot more vacuum advance as well...

HTH

Belden