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350 holley fuel rich running issue

for some reason my holley 350 is leaking fuel in the vacuum chamber behind the power valve making my car run really rich, but still pretty good.
I have a lumpy cam in it, with 107 lobe sep and 287 #50 duration with 430 valve lift.
the vacuum is at 13inch which is normal for a hot motor to have low vacuum like that, so ive got currently a 7.5 power valve.
at first I thought the power valve that was in it was faulty so I replaced it.
then it leaked through again on the new one, and I thought maybe the gasket behind the pv was faulty (coz it split in two when I took pv out) and I put in another pv and gasket, but it leaked again.
So then I did a clean out of the throttle body and the metering plate with carby cleaner and air gun and put all new gaskets through and it ran nice and lean for a day or two then rich as a mutha[Naughty Pottyword]a again. and i pulled the metering plate off and fuel was in the vacuum chamber again.
well Im at a loss.
I know ive got a pretty lumpy cam but can it cause these issues? (just so you know, I bought the cam off ebay and only the duration and valve lift was advertised in the add, not the lobe separation... I only found that out via my engine builder who decided to measure it all prior to installing it and he told me that it was 107 sep. and warned me it was near drag race specs, but coz I needed the motor in my car i said chuck it in so now I have a nice sounding cammy 202 ;)...
well anyway, any ideas on the fuel issue will be great
Thankyou
Grant
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Comments

check that the thread on the power valve insn't bottomng out before the gasket is sealing ,happens alot with non holley pv.may need extra gasket
I'd would try 6.5 pv with 13 hg of vacumn
I run a similar size cam in my with a 500 holley 6.5 pv & 66 main jets

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another question that crossed my mind, the 13hg is when the motor is in park gear, I didnt actually check what it is in drive gear, I would imagine the vacuum would be different, which vacuum reading do I use to figure out what PV to use?
Cheers
Grant

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