Rebuilt carb issues

Posted by Jim Kavanagh On 2018/8/29 0:05:53

In addition to doing a bunch of other things on my '52 250 (327 engine), I rebuilt the carb. Initially, I was getting a ton of gas gushing out of the float vent hole, you could see every time the pump completed a cycle. I lowered the float a could times, which did not help, and then replaced the needle and seat with my original (the rebuild kit had the flat type). This fixed the issue right away. But, I had very bad running/missing at top end and the car was running hot - not overheating, but running hotter than normal. Timing was dialed in perfectly and the car started and ran not under load as good as it ever has.
I re-adjusted the float as it was low due to my earlier issue, but now the car idles way too high and I need to really goose it to get the idle to snap back to normal.
No vacuum leaks, the distributor was not changed and has always operated fine - vacuum advance always seemed to work.
After changing the needle and seat back, I did not do anything with the throttle body, butterfly's, etc. It is not the linkage as when I take it off, I still have the same problem.
I do not have a return spring on the carb, but have never needed one. BUt I need to apply pressure to the throttle linkage to get the carb to snap back to its stop.
I did re-adjust the metering rods, but I am not sure that would cause this issue. I did also re-adjust the idle screws, but this seems really to be the throttle failing to turn to its position on the stop.
Assuming this is the carb, what would the likely cause be?