Some hesitation and stumble 85 k20

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fender89

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Pacific Northwest
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Randy
Truck Year
1985
Truck Model
k20
Engine Size
350
Truck has a holly truck avenger carb, vortex headers, emissions was deleted. Truck runs idles fine, and as long as I drive it like a grandpa it does fine. But when I get on it to accelerate hard it stumbles I also did notice a few very small back fires but those are rare.
I did find a vacuum leak on the intake manifold and took it off put new gasket it a year ago or so which seemed to help. I drove it probably a dozen times over the winter and now it's stumbling again. I don't believe it has any more vacuum leaks, if it does it would be very small. Any holly gurus here? I think it has to do with it but who knows. Any insight would be helpful. Thanks
 

fast 99

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350
Possibly lean, check fuel pressure and volume, float level, accelerator pump, fuel filter, ect.
 

Ricko1966

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What distributor do you have in it? How is it timed? Are you sure you don't have 2 plug wires crossed?
 

Matt69olds

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Is the accelerator pump adjusted right? You should see fuel come from the pump shooters with the slightest movement of the throttle.
 

Ricko1966

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Truck has a holly truck avenger carb, vortex headers, emissions was deleted. Truck runs idles fine, and as long as I drive it like a grandpa it does fine. But when I get on it to accelerate hard it stumbles I also did notice a few very small back fires but those are rare.
I did find a vacuum leak on the intake manifold and took it off put new gasket it a year ago or so which seemed to help. I drove it probably a dozen times over the winter and now it's stumbling again. I don't believe it has any more vacuum leaks, if it does it would be very small. Any holly gurus here? I think it has to do with it but who knows. Any insight would be helpful. Thanks
Was this supposed to say vortec heads? Does the problem go away after the engine is hot?
 

85K304SPD

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K30
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383
HOLLEY carburetor, VORTEC heads and snow in the picture. I dont think the heads don't have a heat crossover. That could have alot to do with the problem. Sounds like it needs a good tune up as well. Just some thoughts.
 

fender89

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k20
Engine Size
350
turns out i changed my fuel filter, and retarded the timing just a touch and the hesitation is gone. i also ordered a non dial fuel pressure regulator. much appreciated on the responses
 

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