Two possibilities come to mind. The first is a bad vacuum advance
on the distributor, though this doesn't really sound like that.
The second is that the low speed jet on the carb is plugged or set
too lean. On TF trucks the low speed jet is adjusted by a screw
near the base of the carb, set at an angle. AD trucks should be
pretty much the same. I would try backing this screw out 1/4 turn
until the problem goes away. Could also be something stuck in the
jet at the end of this needle valve.
Anyways, that is where I would start looking.
Bruce K
57 3200
Mt Iron, MN
At Saturday, 29 March 2003, you wrote:
>Symptoms:
>
>The truck starts and idles well to begin with. After I bring the
engine up
>to temperature (180 degrees) I start down the street and everything is
>working great. Choke is pushed "in" all the way to the "off" position.
>After about one mile the engine suddenly sputters and bogs down
while going
>thru the low end of each gear. If I really give the truck the gas it
>accelerates great and the engine runs smoothly with no hesitation or
>misfiring. If I pull the choke out all the way, engine idle speed
increase
>and the problem goes away. Even at, say, 45 MPH the engine won't run
>smoothly unless I pull the choke out all the way, but under load
everything
>is "zoomerie"!
>
>What I have checked:
>
>Timing is OK.
>Point gap is OK.
>Plugs aren't oily or sooty...they look normal.
>Replaced the ignition coil. No change.
>Checked ignition wires...good spark.
>Checked for vacuum leaks.
>Cleaned carb with some carb cleaner.
>
>Any ideas?
>
>Thanks,
>
>Bruce Marshall
>oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>
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