For the record, the power valve does not affect idle. It can’t. There are videos to prove this out.
Several folks on here have tested it and found that this is correct.
The correct way to set power valve opening timing is 3-4 less that cruise vacuum and then tune the rest of the carb for that.
Also, I’ll point out that if you delay power valve opening more than it should be and it runs better, it’s a sure sign the primary main jets are way too big.
To tune for that, plug the primary power valve off with a plug. Drive the car and get the speed up to cruise on the main jets. Drop main jet sizes until you start to get a slight lean surge and then go up 2 sizes and leave the primary main jets alone. You should never have to touch them again unless a big change is made like you moved to very high elevation, cam change or some other modification.
Once you do that, put the power valve back in and tune for WOT by increasing or decreasing the Power Valve Channel Restricters, which are the holes behind the power valve. And by changing the secondary main jets.
That’s the proper way to tune Holley. For starters anyway.
