[Kennyb]

First let me say what a great discussion this is. I was searching on ported/non-ported and found this thread.
Some of my own thoughts on this thread, Vacuum advance is max when the engine is idling/cruising. Regardless of whether its a ported or manifold connection. the moment you stomp on the pedal the vacuum pressure at the throat of the carburetor drops (instantaneously) to 0. Vac advance is now no where to be found. Also, suction/airflow through the venturis is 0 (instantaneously). To make up for this loss of fuel flow we have an accelerator pump that squirts raw gas into the throat of the carb. as fuel is pulled down through the barrels the and the A/F mix normalizes and RPM increases there is still little or no vac advance because we still have throttle plates wide open. centrifugal advance increases with RPM and we start getting on top of it. Once the secondary open and we get max vac centrifugal advance has/should have done what the vacuum advance was doing at idle. Vacuum advance is fine for street cars but useless in racing.
One last thought, this one about run-on. Throttle solenoids kept the butterfly open just a hair and when power was removed the plate slammed closed and suffocated the engine thus eliminating run-on. Unless of course the timing is so screwed up that the engine diesels just from the super heated pistons.
according to what I have read in this thread I'm not too far off in my thoughts... anyone?? i