My engine is not idling fast enough when cold. I have messed with the fast idle screw by the choke with no real results. What I noticed was that the choke completely closes the butterfly when it is cold (before you start). Is this correct, or should it be slightly open?

thanks,

 

Generally, the choke should close fully when cold (below 60° or so) with the engine not running; and the primary vacuum break diaphragm, at the front pass side of the carb, should pull the blade open slightly once the engine starts.

Make sure that the fast idle screw is actually contacting the fast idle cam; and that the vacuum break diaphragm works. You can push it on by hand, cover the hose fitting with your finger, and it should stay pushed in. If it retracts, it's bad. Once you're sure it's working, adjust it (bend the linkage) such that it cracks the choke blade open about ¼" when the car starts; and adjust it from there. If the car runs REAL rough and blows out black smoke when you try to accelerate, increase the vacuum break (larger gap); if it acts lean, like it stutters or hesitates when you give it gas, decrease it. It's a tuning adjustment, so there's no one "right" setting, although there is a factory spec that should at least be close if the motor is completely unmodified in any way.

 

Great info, thanks.

Now, I have some checking to do.