Compression test results

GREEN GHOST said

Haven't dove into carb tunning yet. Just remember reading as a basic rule of thumb the pv should be approx 1/2 the size of your manifold vac measurement at idle.

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Yes, that is frequently said and is completely wrong. This misinformation keeps popping up (and I think Holley tech is still telling people this). It's only close if you have a very mild cam so idle vacuum is high (and well above cruise vacuum). I suppose they tell the average 350 SBC owner this to keep them out of trouble? :realcrazy:

Idle vacuum has nothing to do with the power valve. Someone already mentioned that a place to start tuning is 3-4 inches below cruise vacuum. Not idle.

My 451 ([email protected] cam) idles at 8" and cruises at 15". A 4" power valve would be very late opening and cause a big lean spot. After extensive tuning I have a 9.5" and it's just about right. :)