just went through my carb , but.............

squeeezer

im probably way overthinking something and ill have to work it out @the track when i find time

so i still run a powervalve and not sure when or why id run just jets in the primaries

so i stage my car at 2000rpm vac is at 11hg
when i gunit of the footbrake it shoots directly to 5hg
i have a 7.5 hg p.v.

how do you guys go about this.......forget mileage(ive been there done that)

dont forget i have that 125 shot i hit off the line as well (powershot)

af2 · Posted: Sun Jun 28, 2009 10:23 pm Post subject:

Sounds like you are in the ballpark. I run a PV in the primaries. I see no reason not to.
Using Smokes calculater I come up with 7.374" on the PV. paranoid

clay · Posted: Sun Jun 28, 2009 10:24 pm Post subject:

Personally I like to run a power valve. Since it's rating is above the manifold vacuum level you have on the brake, it's open and you effectively have the same setup as if you had it blocked and larger main jets. With the power valve it will just run cleaner coming back up the return road, etc. I have seen some tests that do have a little quicker e.t. from blocking the power valve and jetting up. I don't really know why though. All the power valve does in open up a passage from the bowl to the main well. It does pick up fuel a little higher in the bowl, but in the primary bowl this shouldn't be an issue, definately in the secondary bowl if a power valve is used though. I'm rambling now, back to the original question, unless you find it doing something stupid on the launch, I'd leave the power valve in it. Nitrous isn't a problem with it unless you have a huge lean backfire and it doesn't have the power valve protector (check valve) in the base plate. Clay

clay · Posted: Sun Jun 28, 2009 10:25 pm Post subject:

Crap - treed again. That's what rambling will get you.....Clay

10sec.et · Posted: Sun Jun 28, 2009 11:29 pm Post subject:

squeeezer · Posted: Sun Jun 28, 2009 11:51 pm Post subject:

Knarley Darley · Member Joined: 22 Apr 2004 Posts: 1158 537254.14 points

Isn't the power valve doing what its supposed to? Manifold vac above 7.5 holds it closed, and below the valve opens to richen the mixture so it doesn't bog. The only problem is if it closes during the run you are going to be leaner after it closes which makes tuning a nightmare, and if you really want to have the carb sized right, it shouldn't have any, or very little vacuum during wide open throttle. If it has vac during the run you are losing some power potential because the air has to be restricted by the carb to make vacuum, and that restriction is horsepower loss. The carb needs to be sized so the valve stays open during the entire run.

clay · Posted: Mon Jun 29, 2009 6:09 am Post subject:

jeep_406 · Posted: Mon Jun 29, 2009 9:02 am Post subject:

I've always run a power valve in the primaries and don't remember ever seeing vacuum during wide open throttle.

Knarley Darley · Member Joined: 22 Apr 2004 Posts: 1158 537254.14 points

Jeep that means your carb is big enough. We were running a friends 440 mopar with a 750 Holley, and he was getting about 1.5 inches of vac at high rpm under WOT. We changed the carb to an 850 and he picked up slightly on E.T. and MPH. and the vac dropped to almost nothing.

lun40119 · Posted: Mon Jun 29, 2009 2:50 pm Post subject:

squeeezer · Posted: Mon Jun 29, 2009 6:57 pm Post subject:

yeah its a 70%strip 30 %street car

and i do want good street manners

so should i just tune it for n/a ???
or tune it for a 125 shot???prolly the same???

i dont use the stuff on the street......................................as of yet

lun40119 · Posted: Mon Jun 29, 2009 8:26 pm Post subject:

Are you tuning with your a$$ or do you have a wideband. I have tried and tried to get it right, by reading plugs, and all that stuff, but 3hrs on a chassis dyno, cures all fella.

clay · Posted: Mon Jun 29, 2009 9:09 pm Post subject:

240Z8 · Posted: Tue Jun 30, 2009 3:03 pm Post subject: