i have a problem with my holley 750 dp mechanical secondaries.car runs great cold but as soon as it heats up it runs bad and dies.when it does die i need to open the throttle wide open and crank it ,to get it started.I think i might of ruptured my power valve.i have the power valve out of carb, is there a way to test to see if its broke.as far as i can see the power valve diaphram seem to be intact.this car is race only ,so should i just use a power valve plug????another possibility i was thinking was i might be expierancing vapor lock???

 

Are you using a choke when cold?

When it is warm and runs bad, is it smoking? How do your plugs look?

What's your fuel pressure? Are the floats properly adjusted?

The power valve doesn't have anything to do with starting. Sounds like you've got something else going on.

 

I dont use the choke at all.

fuel pressure is at 5-6 psi.
as far as the floats i havent checked it ...get back to u on that one.

when car is hot it wont start without having to put your foot to the floor while cranking.

 

If it runs well cold with no choke, then it's grossly over-rich. It should hardly run at all when cold w/o choke if it is properly tuned for operating temp.

 

Yeah.. sounds like the bowls might be over full and causing it to run rich. opening the throttle all the way is letting more air to lean it back out.

Also consider that if it was fine before you might just have a stuck needle in the bowl letting fuel in constantly.

 

your right. i had my car running,shut it off and checked the float levels.I took out the little screw on the side of the primary bowl, some fuel seeped out,i took the screw out on the secondary and whole lot of fuel goshed out. i adjusted the float lower and lower to no avail.I think i might have a bad needle and seat.the fuel pressure is 7 pounds.