Power Valve Selection: The Definitive Answer

CRUZE 418 said
I will never understand all of the info in the previous 4 pages. Changing power valves from one extreme to another have done nothing for my six pack. 10 ins of vac at idle, 19 at 2500 rpm driving 55mph. Promax rear throttle plate, have tried both the factory metering plates and the ProMax replacements. Found one big mistake that I had made with the ProMax replacements, which started two more problems, start over. I believe that my phasing is off too, stock type mopar dist with FBO module. Testing last nite, engine is backfiring under wot now, and all that I had changed were the vac pod springs. So that is new.
It gets tiring when you think that you know or understand what is happening, but I don't, and I am not totally new to this. I haven't quit, but I am getting tired, and I didn't really want to go 4 barrell or FI TECH injection. I will continue to read and test, keep up with your results!

I plan on trying both ways, myself just for experimentation's sake. I'm going to try both a 9.5 and a 3.5 PV, primarily because I want to LEARN more about how the systems work. My cruise vacuum is 12 hg @ about 60 MPH and about 2650 RPM with my big toe on the gas just keeping it going on a level road. Using that theory, I should use a 9.5 "or so" PV.

However, my idle vacuum is 6hg @ right at 1000 RPM. So with the 6.5hg PV, it's open at idle. With no signal across the boosters though, that fuel has nowhere to go, so it cannot flood, like some people say .....and it's not.

With the 9.5hg PV, it will certainly be open at idle. But the cruise vacuum theory is the closer you can get the PV opening to the cruise RPM vacuum reading, the leaner you can go with the pump shot and main jets.

Crapped if I know any of it, but I plan to try it both ways when my power valves get here tomorrow. I am also going to jet it up a jet size or two on the primaries, as I am experiencing what I think it s lean miss at part throttle cruise. It kinda "bucks" a little at part throttle going down the road. If I put my foot on into it, it cleans right up.