When disassembling the 2bbl Rochester off my '68 350, I found that the choke plate was binding quite a bit. This was not surprizing since I knew by the way it behaved on cold-starts that the choke / fast idle cam wasn't working as it should be, and there was alot of gunk on this. I had to clean off the gunk and use some WD-40 just to get the choke plate out of the slot in the choke shaft to get it properly cleaned up.

What WAS surprizing was, when putting the cleaned-up parts back together, the choke plate refused to slip back into the slotted choke shaft as it has on the half-dozen rebuilds I've done on this exact carb over the last 30+ years I've owned this car. This is when I noted that the choke plate had been scraping against and was binding within the upper carb housing opening / throat (the marks on the carb housing were probably caused more by my wrestling with this to get it apart than by normal wear), as if either the plate is now somehow wider than it used to be, or the carb upper housing is now narrower where the choke shaft goes through causing the plate to bind. I ended up grinding off a slight amount of the sides of the choke plate to get it to slip back into place, and now it moves freely as it should. So my question is, how the heck did the dimensions of the choke plate and/or carb housing/throat change to start binding in the first place?? Can the aluminum carb shrink with age, or can the steel choke plate stretch with age?? WIERD!

 

I had this problem on a 2bbl also. A buddy told me to not over tighten the wing nut as it would warp the area there on top and cause the choke to malfunction and rub the carb body. He recommended I gently peck that area back down a little, maybe I wouldn't see it move but may help. I hit it some, it worked, I do not crank the wing nut too hard, it's working fine. "It worked for me"
Good luck,

 

Aye, I could see how that would pull in the sides of the throat of the carb a tad. I'll be sure to not do that. THANKS!