I have 390 with about 12,000 miles in my truck. Has a 670 Holley, intake and headers. When ever I hit the gas from idle it bogs and pops thru the carb, I have to feather the gas to get it to go with out popping. If I'm crusin under 1500 rpm and I nail it, it will also stumble and pop. What wrong with it.

I Screwed in both idle screws and it dies so i dont think power valves blown and i have the timing set 12 degrees initial.

 

Check in a few lines down.. https://www.ford-trucks.com/forums/s...d.php?t=341609

--Mike

 

this may be a little stupid but quite possibly the problem check your coil the the ciruits aren't in specs it may not be enough juice to spark with that amount of cylinder pressure

 

It sounds like a lean condition. Check your accelerator pump for proper operation. It should squirt gas with the slightest throttle movement.

 

Could be a lean running condition,accelerator pump to sloopy...to much Timing, Or a blown power Valve....If you have an older carb without the power valve blowout protection in it...all it takes is one good sneeze back thru the carb to blowout the power valve......

Russ

 

Another cause could be a vacuum leak. Hook up your vacuum gauge and see what you get. If you are losing vacuum then your engine WILL bog and the extra fuel in the runners will "pop" back through the carb when it does get going.

 

Last Night I changed to a 50cc Accel Pump and all hesitation and popping is gone. I'm so glad I finally got it running right. Thanks for all the help.