We ran across this simple video from Holley that shows the basics of Holley Power Valves and know that for some reason Power Valves seem to have a lot of voodoo surrounding them. There shouldn’t be, but for some reason folks seem to think they are hard to understand, tune with, and change. They are not. So check out this video and get the low down on what you need to know to choose the right Power Valve, check that it is working right, or change it our for another.
If you have questions you can feel free to ask right here and we’ll get you an answer while we are on the dyno. In the meantime you can also visit Holley.com for more info.
You know I grew up on the 1/2 idle vacuum ,proper power valve lesson.But in practice Ive found even with a 8inhg idle vacuum an 8.5 PV works great.My cruise vacuum is 16inhg.
The booster doesn’t see enough drop to pull fuel up the main well at idle so no PV over richness.
I think if I was running (the “correct”) a smaller carb the rule would work but with an 850 on a 430in FE I have no problem.