Classic/Antique Car Repair: 65 Caddy Fleetwood Brougham Rochester 4GC Rough Idle, fleetwood brougham, vacuum ports

Question
Glad that there are people out ther that are willing to help others :-)

Hopefully you can help me with my problem.

I rebuilt the Rochester 4GC Carb on my 65 Caddy with the 429 cu.in. engine, as it had a rough idle.  I still have a rough idle.  It might have been rebuilt before but I am unsure.  All Ignition parts have been replaced, except distributor.

I used new gaskets that looked like the old ones however, I noticed that the Throttle body to bowl gasket has some notches in the secondary bores, but also has them in the primary bore that the kit instructions said are "Vapor Vent Passages"

Now on my carb, these notches are not being covered by any part of the carb and seem to letting air into the carb resulting in the rough idle.

Even the Cadillac Service Manual shows these notches on the gasket.

I unplugged and covered ALL of the vacuum ports to make sure the were no other leaks, then I started pouring water around the carb, and sure enough, it is letting in air right where the notches are in the throttle body to bowl gaskets primary bore.

Is this right?  I bought 2 kits, rebuilt the carb twice, and both kits had the same gaskets with the notches.  Am I missing something here?

I hope you can help me.....

Answer
The 4GC kits are notorious for this and other problems.  You are exactly right, there should be no path for air to enter the intake stream that does not take it through the air cleaner.    I've fought exactly the same problem with the 4GCs on Packards.  

There are also two sizes of accelerator pumps, and the kit manufacturers seem to put the wrong ones for the application in many of the packages.   I've had better luck with NAPA kits, because they usually include gaskets etc. for all the variations of the 4GC.    If you have a good kit, and you can't find the gasket that will close all the passages to the outside world, the only other recourse is to get a kit from  Jon Hargrove - contact them at "The Carburetor Shop" at www.thecarburetorshop.com

Congratulations on the detective work - you really don't need my help anymore - you did exactly the right thing.     

Dick