carb rebuild

[Black Smoke]

After rebuilding the carb yesturday my truck runs better for sure. One thing, it idles extremely high even though there is no solenoid and the idle screw is backed out and the high idle is not engaged, or otherwise interfering.

If I hand apply force to close the throttle it slows down, but not on it's own. Any ideas? I have also adjusted the timing and the idle mixture screws. Springs are all attached properly to the throttle as well and vacuum lines are correct I believe. Could the float be set wrong? ???? I am stumped, I sure hope I don't have to take the carb out.

[PhilSine]

This reply is also on the mailing list in case it looks familiar.

Just this last weekend I was finally able to settle my idle back down after I did a rebuild of the carb. It was up around 1100 RPM and I couldn't figure out why or how to get it down. I should mention that the situation was the same as you described. Idle screws adjusted, timing right, stop screw backed out.

First, I adjusted the choke. That was a separate problem as far as I can tell. I made sure the choke was closing the butterfly when cold and opening it when warm.

Then I screwed the idle screws in all the way (both of them) and backed each off 1/4 turn. With them in all the way your Jeep may stall. If it does, back em both out 1/8 turn and start it up again. At that point back them both out another 1/8 turn and see where your idle stands. If not low enough, do another 1/4 turn on each screw. Continue this until the idle settles down. I wound up with about 2 5/8 turns out on each. When I went too far, I clearly noticed the exhaust getting thicker in reaction to the richer mixture. At that point I started screwing in 1/8 turn at a time until the exhaust smoke thinned. When screwing in, if the idle goes up again, back it off a bit until it settles down again. Each screw must be turned the same amount and in small increments.

My Jeep now starts up without touching the gas, cold idles at 200 RPM without dying (even when I drive off with it cold) and idles at 700 when warm (normal according to spec). It will idle at 550-600 when in drive.

Good Luck. Hope this helps.

P.S. The first dip in idle at about 3/4 to 1 1/4 turns is probably not the final setting. Keep backing out slowly. The amount of turns for each carb will vary. Mine is a Holley 4bbl but the 2 extra barrels don't affect idle.