graemlins/beers.gif I recently installed a 750 Dbl. pumper on my car. I was driving the car recently and it lost its ability to idle! I was wondering if there is a technical way to check the power valve? Do the double pumpers have two power valves? It runs Great at wide open throttle, Just won't idle!Seem to load up when you let it idle! I also thought that it might have some dirt in the needle and seat so i took it out and ran it through the gears!Still there though!! Thanx!!!!


1970 chevelle silent sleeper
SBC powered jap trap eater!!! graemlins/beers.gif

what do you have your fuel pressure adjusted too? , and have you ck'd float level?

Fuel psi. is fine and i have not adjusted the float level! Although this carb has been on the car for about six weeks and never caused any problems till now! That is the only reason that i have not checked float level yet! Beings the carb does not have a choke on it and it does backfire every once in a while i think that the power valves have gone south?? I am going to take the carb apart and look at it and see if i can see anything obvious! The double pumper kit is real inexpensive so i might go that way and install a power valve saver as well!! Any experience with these as far as their dependability (power valve saver that is?)i have installed them before but did not know if they work well or not?? graemlins/thumbsup.gif Thanks!!

i had something similar happen to me but my carb wasnt a double pumper, my meter valve had a little piece of junk in it, cleaned it out, only took a min. and it ran perfect, might want to check that. dont know if that helps at all.

Jeff,a bad pwr valve will make your car idle rich but it will still idle half way decent if it's blown or the wrong one for lower idle vacuum with a perf cam.

You likely have a piece of contam/dirt in your idle circut and or your idle bleeds up in the venturi.

You could also have a problem with a shrunken gasket inbetween your metering block & main carb body thats blocking the idle circut on one side. I have seen this mult times on Holley's with the older/obsolete gaskets that were junk and shrank
always causing problems/leaks. Holley has since come up with a new gasket design to correct this issue.

Clean the bleeds out and remove the idle mixture screws and spray some carb cleaner through all of them.

Then Re-install/adjust the idle mixture screws and if you still cant abtain a idle decent then
i would opt for a carb rbld.

If you have an idle mixture screw that seems to be inaffective or only changes your idle a little when compaired to the other idle mixture screw/s then that tells you it's likely a carb/idle circut problem and to go after that with a carb rbld.

There is a remote possibility your pwr valve's vacumm rating is incorrect for your cam's idle vacuum and over time the extra rich idle mixture
has fouled a plug or two leading you to think there is a carb/idle issue when in fact it's something else altogether like a fouled plug.

There are a lot more things this could be(bad wires/cracked cap/broken valve springs/bent valve/vacuum leak/etc) but lets stop here for now and see what you have after you check these things out.

Scott