I rebuilt my Holley 750 double pumper and now it bubbles raw gas out of the primary boosters when the motor's running--not when it's off but the fuel pump on.
Float level is correct, needle and seat are working, new power valve installed correctly--no fuel dribbling from the squirters so the accelerator pump circuit is OK. What's going on?

 

Not sure what "when the motor's running--not when it's off but the fuel pump on" means, but that is a symptom of:

a) Float level not set correctly, or;

b) Needle and/or seat not working correctly.

 

Thanks for the reply. What I meant was, my fuel pump is on a seperate switch from the ignition so I can turn the fuel pump on when the motor isn't running. I wasn't very clear.
With the fuel pump on and the fuel system pressurized there are no leaks--needle and seat work fine--but as soon as I start the motor and the carb gets vacuum , raw fuel starts bubbling out of the boosters--enough to kill the motor. It does this with the float level plug on the side of the bowl removed and no fuel is flowing out the hole--the needle and seat are working fine and the float level is set just right, but the boosters dump raw fuel with the motor running--wierd. Some passage is blocked or something.
I'm taking it in to a pro drag racing buddy tomorrow morning to see if he can figure it out--I did something wrong when I rebuilt it, but darn if I can find it.

 

rb',
when you rebuilt the carb,
did you monkey with the primary metering jets?

 

You've got the idle speed screw set so that its holding the throttle open too much. It should be set so the transfer slots are exposed no more than their width. You have to have the carb off and look from the bottom to see this.

If you have to open the throttle more than that to keep it running, your idle mixture circuits aren't right (either plugged, or not properly adjusted).

 

Problem resolved: I got this carb from an old friend last week, one he'd had for years. I remembered it used to run great but probably just needed freshening up. It ran OK when I got it but wouldn't idle, like plugged circuits.
Well, I took it to a professional drag racing friend this morning--he took off the primary bowl and asked, right off, if the float had been adjusted way down when I got it, then if I had adjusted it up to the proper level when I rebuilt it--yes, that's just what I'd done.
Well, the bowl gasket was pink, which meant it was for an "HP" series Holley, not a double pumper like this, and the holes in the gasket for the boosters were much too big--but if you adjust the float way down the gaskets would work--an old emergency drag strip fix. So he put a set of blue double pumper reuseable gaskets in there, I brought it home, dialed it in and the car runs fine.
Thanks for the help--I did check those idle circuits and the slot in the throttle plate like I was advised--thanks.