289 2 barrel carb - auto vs. manual?


New Member
Apr 8, 2019
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.
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SN Certified Technician
Apr 12, 2002
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.