Sounds like the rings haven't yet seated? Did you degree the cam or just match the dots? IIRC, and it's been a LONG time, Holley's come with a 12.5 HG power valve and you're only pulling 10 HG? So the PV is open the entire time you're idling?
PV enriches the mains only, not the idle circuit. Doesn't matter if it's open at idle or not.
My 451 idles at 8" Hg and the idle AFR and RPM stay the same whether I have a 10.5 or 7.5 PV.
Incidentally there's another urban legend, which Holley is
still perpetuating, that your PV should be 2" below idle vacuum. Which is pure bull. You want it to be several inches below
cruise vacuum - the exact point has to be determined by experiment and a wide-band AFR meter to assist.
My cruise vacuum is 14-15", and I'm still trying to decide whether the 7.5 or 8.5 feels better on the butt-dyno. I tried a 10.5 but it was coming in too early, just making things overrich. Remember you want the mixture to go
leaner at part-throttle, until somewhere above 50% of max power (this point on the curve is different for every engine and induction system).
