I have a 1986 F150 with 5.8L and a stock Holley 4180 carb. The carb was leaking at accel pump so I re-built entire carb. Ran good for a day or so then started a major hesitation while accelerating through entire primary range. It will stall unless I feather the pedal. If I open the secondaries it will go. It happens always under load and I can make it happen in park. Any ideas? I replaced the float seats, powervalve everything internal. Did not remove the needle valves because they are capped and not in the kit. Help

 

When you rebuilt the carb did you put a different squirter in it? Sounds like its going through a lean stage.

 

If it runs poorly "while accelerating through entire primary range", it isn't the squirters.

Accelerating only? Okay in cruise?

I'm not that familiar with the specifics of Ford Holley carbs. But, the general principles should apply.

 

I did not change the squirters. This is an OEM carb. Yes it runs poorly through the entire primary stage on acceleration. When crusing 45 or higher it seems ok. If I hard accelerate into the secondaries, it is much better. The carb has primary & secondary float bowls. Should I pull the primary float bowl and re-clean the passages? The filter is a copper type which I also changed. The needle valves are capped so I did not touch, they were not part of the re-build kit.

 

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Once, after a rebuild, my carb ran extremely poor when just using primaries and below 1500 rpms. Turned out the carb was set way too rich. After leaning out the idle air bleed my carb preformed much better.