I got your answers to my good/bad power valve post, and now my question is this. (( I came from 4'000 foot hight to 300' foot hight, aprox 3700' foot difference)) If I replace the P/V, should I go with one that is smaller (ie:lower # on the front of it) or bigger, or stay the same size. I dont know what I have in it yet. Running a Holley 750 DP on a pumped up 440. Thanx..

You want a power vave that opens at about 3 inches of vacuum less than what your engine idles at ( in gear if it's an automatic ). In your case, you will want to go up in size ( numerically speaking ). Most 750's came with ether a 6.5 or an 8.5 PV. If I was you, I would try it like it is first. Cruise down the road at a steady speed and then dip in to the throttle a bit. If you don't experience a hesitation or flat spot. Your PV is probably ok as is. You would be more likely to experience a problem if you went from a low altitude to high.

Best way to figure out which power valve you need, you need to see how many inches of vacuum you are pulling at cruise, and idle. It all depends on how big of a cam you have. I have an old school MP .509 lift cam and I can only get about 4 inches of vac, so I got a 2.5 pv in.