1958 Cadillac Rochester 4 gc carb. Won't IDLE !

[fleajr]

My 1958 Cadillac Fleetwood had a rebuilt Rochester 4 gc 4 barrel carb. installed recently. My mechanic says that the engine runs very irradically with the new heat insulator and gaskets installed on either side of it. So, he ran the car with only the 2 new gaskets and NO insulator and the car ran quite well. Problem now is the car will NOT IDLE at all!  He sprayed carb. cleaner around the carb. areas with the engine running at fast idle and the engine did not speed up at all , meaning there is no air leakage?  Could it be a vacuum leak and where should I check first?  Do I need the heat insulator installed under the carb. or is it ok to run the car with only the 2 new gaskets under it?  Anyone in the Cadillac Club or?  have any ideas of what the problem is or who I can contact to help with this will not idle issue?  Thanks, Al

[TexRiv_63]

The heat insulator is not a bad idea in this time of ethanol gas but raising the carb up could cause linkage adjustment problems. As far as the idle problem it could be a poor rebuild job using incorrect gaskets. I learned this with Oldsmobiles using the 4GC carb, the "universal" rebuild kits come with a bunch of similar but slightly different gaskets, if they are not a perfect match for the originals they can cause all kinds of trouble. Incorrect float settings can also cause problems. Good luck!

[GARY F]

an off the wall shot. when i put my 63 bonne back together mine would not idle.  I loosened the 4 nuts on the carb and moved the carb back toward the firewall with the tiny bit of play in the bolt holes. It has been idling nice since 2001.  Like I said an off the wall shot.

[padgett]

In a fresh rebuild if the gasket trick didn't work, I'd be checking for clogged idle passages, used to find them all of the time in older carbs.

 

BTW shouldn't a 63 Bonne have a Carter AFB and not a Rochester 4GC (totally different carb) ? Think the only Rochesters in '63 B-bodies were 2G and 2GC..