My guess is that you are boiling the fuel in the float bowls, and it is spitting out of the float bowls and flooding the engine when it warms up. Seen this a few times before. Boiling point on today's gasoline is really low. For a test, you can empty the tank and put in 5 gallons of race gas, which is leaded and will have a much higher boiling point. If that solves the problem, you need to start thinking about a return style fuel system, and insulating the carb from heat, and the fuel lines from heat.