Holley Street Avenger 570 Idling Problems

Mattax said

As far as getting full vac on your ported source, Holley tech was logically guessing. The port is located just above the throttle blade's idle position. At idle the nearly closed throttle creates the pressure drop which is the manifold vacuum. As the throttle opens past the port, the port becomes exposed to the manifold vacuum..

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When any port above the throttle blades (ported) start to pull, Is it the vacuum from the intake that is now being "seen" or is it the fact that high velocity air traveling over a tube end pulls the column from the tube? Thought it was the latter, like the vacuum secondary of a Holley 3310, only opens when secondary air passes over the vacuum put inlet. Either way, I would get the front idle transition slots perfectly square and then adjiust the secondary throttle stops to get desired idle, not the throttle stop.