Possible Vapor Lock
I believe im having some vapor lock issues too, but after shutting down, the motor heating up then trying to start again it will start fairly quickly but will not run at an idle(my 318 has 360 manifolds on it that come with in about 1.5-2" of my fuel line and i have a mech fuel pump. im assuming your situation is that once you start back up it will run fine? someone told me that my problem would be fixed with an electric fuel pump because it is always forcing cold fuel through. this is a shot in the dark but maybe if you engage the fuel pump for a few seconds before starting it will be able to clear the lock it self with just the fuel pump? good luck