Carb/timing procedure

Some guys DO use manifold vacuum for advance, I do not. But I would say that you are likely going to have to "rough it in" with the vacuum disconnected, OR "rough it in" with a hand vacuum pump activating the vacuum can. This first, seems to me, is because when the thing is "running normally" the manifold vacuum will be high and fully advanced the vacuum can. ----- This is all because as you tune the carb, the vacuum is obviously going to change, and the TIMING will then change, which will then affect the idle speed. You could get yourself into a "feedback loop" where one changes, the other changes, and the first one changes because of it.