Manifold Vacuum Experiment

Let me add to this thread. I can't give numbers as I did this about a year ago as a "crutch" to make my car drivable. 64 valiant 170 slant 3sp stick. 9.5 - 1 CR, mildest Mopar performance cam, electronic dist (don't know the curve) Holley 1920 carb single 2 1/4 inch exh. Needed a lot of initial timing to get a decent idle, but engine would ping badly when accelerating (ported vac advance). As a band aid I connected the vac to manifold vac. and retarded the initial/total by rotating the distributer. This limited the total and stopped the pinging, but allowed more timing at idle so it wouldn't stall or need the carb opened too far. I can't add any more to this as the car is laid up for body work.