I think we know it isn't. Out of the box, and adjusted according to instructions in most kits, the "gap" creates a dead spot. I always eliminate any gap in the linkage to the acc pump lever. A test is to, (with the motor off) look into the carb. Move the throttle shaft ever so slightly, a 1/16th of an inch should make the nozzle squirt. If it doesn't, you will get the lag, bang/pop, which by now has more than likely blown the power valve, (unless it has a P/V guard poppet)...The fact it doesn't do it for 10 minutes or so says the choke is still creating a fat condition. Once the choke opens all the way, it is too lean off idle.. BTW, check the choke stove/thermostat as it should open sooner than that......The factory gap is to be sure the acc pump lever is in "full ****", allowing the acc pump to fill completly, so carefully loosen the spring loaded bolt/nut until it just touches the lever at rest........There are also different acc pump cams to deliver more sooner, or more later, or a long overall shot. Holley sells the cam kits seperately, and most "trick" kits have an assortment of cams and nozzles for fine tuning............Hope this helps you....aMP

 

Sounds like the vacuum advance diaphragm is ruptured, have you checked it for function and is the vacuum hose connected and tight at the vacuum unit and carb?

 

i have checked the vacaum adv. and it is working. also i have a manual choke and i dont use it so the choke is not the problem. the acc. pump could be it since i just put the carb on and didnt adjust anything. the carb said that it was ready to go out of the box but i guess i shouldnt of believed that!

 

i checked the acc. pump and as soon as you move the thorttle gas comes out. i can tighten or loosen the spring but i dont know if that would help?

 

on my lunch break today i went out and was messing around with the truck. i notice that the idle was alittle rough so i adjusted it. after i did that the truck ran alot better and didnt backfire. it does still have the problem like its not getting enough gas. when i give it a little gas it is ok it just after that when i maybe move the pedal down at most a half inch then it starts in. i then continue pressing and it goes away. it feels like there is a flat spot and it only does it at that point and not any other time.

 

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Did you check your power valve yet???? Or do the things that we talked about already?????

 

no i have not checked the power valve. its a new carb and all of you said it has a check valve before it

 

That "flat" spot you're talking is the exact point where the fuel from the accelerator pump has been consumed and the main metering hasn't yet caught up i.e. the mixture is too lean. I believe your power valve is working as it should since there is no problem after the throttle is pressed past that "certain" spot.
I believe the "cure" can be had by adjusting your accelerator pump/cam/linkage. You need a BIGGER, LONGER SQUIRT! I doubt the power valve is the problem as newer Holley's generally are immune to blowouts unlike the oldies. Also, their jetting tends to run rich, so I don't suspect it either.
It's either that, or a vacuum leak...

 

You need to check to make sure!!!! Use a propane torch!!!!!!

 

i checked and there seems to be no vac. leak. i used the propane torch like you said.

 

how do you adjust the accelerator pump/cam/linkage?

 

At what rpm is the mechanical advance beginning to advance?
Your float level correct?
"Ready to go out of the box", yeah right.