I have 700 holly double pumper that is shoot fuel out of 1 of 2 tubes that stick up from the top of the carb that seem to b hallow

neither
it is very possible to over fuel an engine and that puts the fire out regardless of the power required so extra carbies is not the answer
a single 4 barrel 650 -750 double pumper will do as well if not better than 2 carbies
if you want more hp , turbo it , change the cam to a torque cam, tuned headers , proper balanced exhaust system, top quality ignition system
if you want to be an all out rev head and make the engine as hot as possible , fuel injection is the way to go along with a high rpms cam

Hi!
It seems your fuel pump fails at idle speed. I would first ensure that fuel pump is well fitted, no leaks, and good diaphragm condition.

Larry we need a detailed question and RE POST
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where the fuel line goes into carb the line goes into a big nut remove line remove nut /bolt filter is behind that

I don't see why it wouldn't. If there both 2 barrel or 4barrel it shouldn't matter. How ever you do have to pay attention to how much fuel the carb delivers. Like 750 holly or a 650 holly. Some 351modifieds used a Ford carb and I can't remember how much fuel they deliver. You get to much fuel to your engine and it will put out black suet from the tail pipe. This can cause damage to the piston rings over time. The tail pipe should look white or tan in side if the fuel mixture is right.
I hope this helps, I have been a ford owner and mechanic for years.

it should be on the air horn.

The good thing about a Holley carb is they can be custom built to just about any engine.
The bad thing about Holley carbs is you can work on it for months trying to get everything adjusted right.
You'll have to figure out if it is a lack of fuel or too much air coming in.
The accelerator pump travel can be adjusted up or down as well as the power valve.

probably need to replace power valve in carb

you could try running a fly cable from the battery terminals directly to the fuel pump,that way you know the problem is somewhere in the middle and by moving the flylead forwards, isolating the problem.use small crocadile clips is easiest connectors.saves all the hassle of trial and error(relays,switches etc...)there should be a relay for the fuel system but i cannot remember where,sorry.

You are correct, there is a float inside a holley 4 barrel fuel bowl.
Is the electric fuel pump regulated? If the fuel pressure is above 8 lbs, you could run into this issue or the float / needle / seat could have a problem or miss adjusted.

By the way, a 2007 GMC is not carbureted so I assume this is not the vehicle or it has been modified.

Good luck.
Regards,