power valve help
 

iam trying to tune my 302 i put a vacuam gague on the top of the passanger side of the carb.[on the side of carb.] it reads 6 in. i put a 5 power valve does that sound right. its a 700 df dp 70/ 78 jets to see what my motor has in ti go to rons.mustangii.net

3.0
 

Personally, I don't want my power valve to come in before about 3.0 , I want to cruise at 70 solely on the primaries and no PV and no secondaries, But mine is a street car.

You seem tp have a much more aggressive set up than me. If you need more mixture at an earlier time, then go fpr it. Power valves are cheap. I would just expieriment. It only costs a few bucks for each power valve.

Rev

i was just trying different things to see what happens

I'd write down the vac pres at various rpms. 1500,2000,2500.... etc then find out where in your rpm range you want it to open up. and set the power valve accordingly.

thanks i will give that a try.

The only vacuum port that I'm aware of on the passenger side of your carb is the one used for vacuum advance, which is ported vacuum, rather than manifold vacuum. Make sure you are reading manifold vacuum when you try to figure out where your vacuum is for the power valve.

i checked the manifold vacuum it reads 15in. so what size power vavle do i need, thanks ronnie

You need to check the vacuum while you're driving. Watch how low it gets while you cruise around without getting on it. Then see how low it goes when you start to get on it, but don't actually floor it. You want your power valve to open at a vacuum below the lowest cruising vacuum, but above the reading from when you just start to get on it. In other words, if your lowest cruising vacuum is 10 inches, and it's around 7 inches when you start to get on it, you should get an 8.5 power valve. If your numbers are lower, adapt accordingly. Odds are a 6.5 (65) would be just fine.

On the floor?
 

My theory is that you don't really want it untill your almost on the floor. I run the leanest primary jets that I can. Put in whatever puimp shot is needed for idle to primary transition. I then set up the power valve and vacuum secondaries for maximum power at WOT.

What I'm after is maximum economy at cruise and maximum power at WOT. It's true some compromises have to be made for decent transitions while street driving. That's what I like about Holleys, Demons, etc. They,re modular and can easily be customized for what you want.

Rev

thanks for the info, i put a 6.5 p/v. in and 72/78 jets.iam going to run it next weekend and see what happens.