powervalves
 

seems a lot of people dont run them on there drag cars, was told at least, I should block back powervalve and jet up 6-8 jets, was told I could run front to clean up off idle mixture. I like to get a lot of input so give it to me, for dragracing do you all plug powervalves or at least back ones on a double pump. This is mainly a bracket race only, streetlegal blazer very lil street use!!!

I prefer to block off the power valve on my carb but I dont up as many jet sizes as most would. I bracket race and dont i dont run on the street and in bracket racing you want to be as consistent as possible so I run as lean a mixture as I can get away with which helps when the night gets cooler the car doesnt pick up as much with a leaner mixture. You have to play with your combo to see what works best for your application. All the Holley carbs I have run (all double pumpers) dont have power valves in the secoundaries not sure what your talking about there.
I would plug the primary and go about 4 ot 5 jet sizes up and go from there for track use but if your on the street you can go a few more, like I said before you have to play around with it to see what works best for your combo.
Goodluck, Charles

double pumpers come with a front and a rear powervalve, dont they, that was what I was talking abought

I don't know what other peoples opinion are, but in my opinion if you are racing, the powervalve does nothing. I mean if you have a 3,000 to 6,000 converter it's going into WOT from the get go. The power valve only pays attention when you leave the line at idle and opens up when the vacuum reaches what ever the power valve is IE: 4.5 7.5 for additional fuel. i personally donot run Carbs on any race engine but for the street the a power valve comes into play. If i were racing only i would block them off, for the street i would use a 4.5 let the fuel get there as soon as posslible.

just my .02

Zip.

Most only have primary power valvles but some have secoundary vavles, the consideration would be the if your going to race this set up or drive on the street, if your going to race it and you have a big cam the power vavle wouldn't be much use to you on the track, but if your driving it on the street it can be a big help.

Problem is that the rear power valve will lose contact with the fuel when the car leaves the line
Much the same way as the rear jets do with out jet extensions power valve ¾ in higher on the metering block

Joe

yes a while ago when I got my new carb, found out it didnt have one in rear, so far have foot braked race and was told if footbrake leave it in, if racing with a transbrake or 2 step take it out

SO HOW DO YOU REMEDY THIS STREET DRIVEN THING WITH 4 CORNER IDLE ? CLOSE DOWN THE BACK BUTTERFLIES? AND RUN YOUR IDLE ON THE FRONT ONLY? CAUSE THE BACK WORKS LIKE THE FRONT,AND WITH LOW VACUUM AND A REAR POWER VALVE, IT WILL OPEN AND CLOSE FOR THE STREET BUT WILL STARVE AT THE TRACK,,AND WITH A PLUG IN THE BACK, IT WILL GET MORE FUEL AND RUN RICH ON THE STREET

This is the setup used on an 850. Block off front and rear for drag race (transbrake). Leave the front 4.5 PV for No E. This PV size might very depending on the engine combination. Sqaure the jets front and rear for racing. 80 or 82 is a good sarting point, but again will very slightly according to engine combination. For the street 72 or 73 front and 83 or 84 rear. This was the setup on a 408 CID SBC making about 600HP. Your exact setting may be different but this should be in the ballpark.

:wink: