[SuperHart]

Nope, ain't true. The coolant expansion tank sits off to the passenger side of the engine and should clear the distributor. You might have to monkey around with the direction the vacuum modulator faces but it should fit. Considering the number of times this ported versus manifold vacuum question rears its ugly head on this forum, it's obvious that hardly anyone had been able to figure out the really correct answer to the question.

In the old hot rod days, no vacuum advance at all. Total advance was therefore initial only at idle and at WOT the sum of the initial advance plus the built-in centrifugal advance. Then came the vacuum modulator whose purpose was to provide vacuum advance at idle when the motor was under no load at all, therefore no ping. The vacuum advance was usedto result in a smoother cooler idling motor with reduced NOx. Vacuum at idle was initial plus vacuum (modulator connected to manifold vacuum), advance at WOT was initial plus centrifugal. Advance just off idle was initial only since manifold vacuum dropped cancelling out the vacuum advance and engine RPMs were insufficient for centrifugal advance to begin registering.

Just for kicks I tried connecting my vacuum modulator to ported vacuum and the engine idled like a tumbler full of rocks. Connecting it to manifold vacuum smoothed everything out and dropped coolant temp at idle. Of course, I had to readjust the idle speed screws but, for me, manifold vacuum was the way to go. With ported vacuum, the total advance at WOT was 10* initial plus 26* centrifugal plus 22* vacuum. WAY too much advance.