accelerator pump adjustment
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accelerator pump adjustment
I have a '85 F-250 with a 460 A/T. I put on a 770 holley carb and am trying to make adjustments because it has a slight hesitiation. I have adjusted and traded out carb parts all over the place-smaller jets, power valves of all sizes, choke adjustments, etc. From the advice I have gotten from this forum and other mechanics, it sounds like a a problem with the accelerator pump. I have tried different color cams, adjusted the spring, and tried multiple nozzle sizes. Is there any other adjustments you can make? What other than a carb can be responsible for a hesitiation? Any help would be appreciated.
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Joined: Jan 2001
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From: Virginia
Sometimes it's hard to differentiate carb problems from ignition problems. You have certainly covered the carb from one end to the other, so I think I would start looking at the ignition system.
Check the timing with a light.
Check the vacuum advance unit by revving the engine and unplugging and plugging in the vacuum line. With the timing light on the scale, you should see the timing jump back and forth.
Check the advance weights in the dist. Unplug the vacuum advance, and then rev the engine up and down, and you should see the timing advance and retard.
Pull the spark plugs. Check the gap and make sure it's in spec, and the heat range/number is correct.
This hesitation. Is it more like a bog and is long and drawn out as long as you hold the gas pedal down, or is it a little blip that quickly goes away, even if the gas pedal is held steady.
P.S. What type of intake manifold are you running?
Check the timing with a light.
Check the vacuum advance unit by revving the engine and unplugging and plugging in the vacuum line. With the timing light on the scale, you should see the timing jump back and forth.
Check the advance weights in the dist. Unplug the vacuum advance, and then rev the engine up and down, and you should see the timing advance and retard.
Pull the spark plugs. Check the gap and make sure it's in spec, and the heat range/number is correct.
This hesitation. Is it more like a bog and is long and drawn out as long as you hold the gas pedal down, or is it a little blip that quickly goes away, even if the gas pedal is held steady.
P.S. What type of intake manifold are you running?
