Originally Posted By DaveRS23
Holley has said for many years that half the idle vacuum is the recommended opening point for the power valve. Why that has never been updated is beyond me. shruggy

First off, there is no vacuum signal to the power valve at idle. So, it's relevance to the power valve is questionable. More important is the cruise vacuum. Going from 15" to 6.5" before the PV opens is a long way. Too long in my opinion.

I personally have never seen a PV open too soon on a muscle car, but I certainly have seen them open too late.

So if it were me, I would put a power valve in that opens somewhere between 8.5 and 10.5. No matter what the idle vac is.

twocents


No vacuum signal to the power valve at idle, sorry but that is INCORRECT. The power valve has full manifold vacuum to it at idle. If it didn't it would be open. The power valve gets it's vacuum from a port in the baseplate, not the carb boosters. Once the manifold vacuum drops below the power valve rating the spring in the valves opens it. Just look at the chamber in the carb for the power valve vacuum side and notice the port at the bottom of that chamber and where it goes, it goes directly to the baseplate and subjected to the manifold vacuum.

Last edited by GODSCOUNTRY340; 12/20/17 01:10 AM.
I love the smell of Deer guts in the morning, it smells like... VICTORY!