[BarryGMC]

The hot day shutdown sounds like a vapor lock. Today's gas has a lot lower boiling point, especially the cool weather blends with a lot more butane. This gas workes fine in a pressurized system with a return line but is somewhat problematic in a carb set up. I have a 58 chevy 348 car that is so sensitive to this when it's warm if there is any winter blend fuel in the tank, that I now run any gas out in the spring before it gets hot. The sputtering in my opinion is probably something in the carb that is randomly blocking a jet. I see this a lot. I have 11 pre 1972 vehicles with carbs and points ignitions. Rarely do I have an ignition issue. But carbs need constant attention. Barry