Classic/Antique Car Repair: Engine Stalling when warm, vacuum leaks, 67 camaro

Question
Hi,

I've got a 69 Pontiac GTO with a similar proplem to your recent inquiry about a 67 camaro 350. Mine also stalls, but ONLY when the engine reaches normal operating temp. It will start OK directly after stalling but, since it is warm, the engine will oscillate until it cuts-out/stalls again. No issues whatsoever when the engine 1st starts at cold temp

Its mostly stock, except the mechanincal choke is forced open with a spring, as well a converted points distributor to a HEI from a 75 Trans Am, and aluminum Performer Intake.  


I've placed 2 reman'd quadrajets on it and that didn't solve the problem. I don't think its a sinking float.
I've sprayed around the intake to locate possible vacuum leaks, and found no indication of any.
It's a M-21 4-spd, so no vacuum issues there.
I've tried 2 ignition coils.  
I've installed a 1" phenolic carb spacer to minimize heat transfer to the carb.
Because of it's dependence on HEAT, I've ruled out any problem with the fuel line from the tank to pump.


Your thoughts? Possibly faulty ignition module, fuel mixture, mechanical fuel pump, etc?  

Thanks much.

-J

Answer
Your car starts right up after it stalls and that should indicate that it is not a sinking float or a heat effected module. What I would like you to do is get a spray can of carburetor cleaner complete with the straw nozzle. With the idling spray around anywhere that there could be a vacuum leak. When you find a leak the engine speed will change. Then drop me a line and we will go from there.
Brad