289 2 barrel carb - auto vs. manual?

cubnut

New Member
Apr 8, 2019
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san Diego
Nice 1964 Mustang with 1967 289 convt 4 speed. It has been smooth for decades. Had the carb rebuilt, and now not smooth. Bolted a carb from my automatic, and erratic idle - sometimes 800 rpm, sometimes 1400.

Bought a Chinese carb - chump change; I could risk it. That carb rolls at idle between 1000 and 2000 rpm. Idle jets don't seem to be the problem.

So I think my problem is I don't really understand all the extra stuff hanging on the throttle shaft. There is a lever on the left that appears not connected to anything of importance, and so much stuff on the choke side that I am tempted to go manual choke.

Looking for guidance. I have successfully rebuilt simple carbs, but not sure what is going on here. Will probably return the Chinese carb, and spring for a $400 version, but don't know how to ask for the version without all the dashpots and levers.
 
an automatic carb has an extra lever for the kick down linkage. it can just hang out on a manual trans with no problem. the choke linkage operates the fast idle cam, and needs to be free to move properly.

your idle speed issues can be a result of the fast idle linkage not operating properly, or a vacuum leak, or both.