Silly Timing ???????

I dont know were the rumor started that vacume advance vac source is Ported . BUT its wrong. You always set initial with the vac hose disconnected because if you didnt the distributor would be adding extra timing. And thats with vac hose to manifold vacume. If it were ported vac it wouldnt matter as there is no ported vac till you are off idle. Next you want the vac advance to drop off as load increases and rpm rises or you get detonation. If its hooked up to ported vac. It will pull in more timing plus the mechanical. Giving you a total of some were in the 50s and thats way to much timing under load.Vac advance is a milage thing for light loads and crusing when the vac is high.Some smog cars had a dual diaphram advance unit that had both ported and manifold vacume to it. Those were to retard the timing under certain conditions but that is the only time you hook ported vac to a vacume advance unit.