Vacuum Advance

If you can lay hands on a timing light, you can "Map" the advance curve, with, and without, the VA connected. There are also 2 manners of hooking it up. Ported vac and non ported... get a note book. Or you could just go by seat o' the pants, sound, but not always the most accurate. The thing is you want to run proper initial advance for your motor but you don't want the vacuum advance to kick in too much, and end up with engine damage from detonation