[Tom Wells]

Sledge,

I fought this on the Cobra and a subsequent car for years - literally. Their symptoms were essentially identical to yours except occasionally after a good high speed run the idle would go away and the engine would quit suddenly.

The solution was to switch both cars to fuel injection.

The reason for the problem as far as I have been able to determine is the low vapor pressure of the substance we now laughingly call gasoline.

When the lead was removed and alcohol introduced, the boiling point of "gasoline" went way down - at least for the alcohol portion.

I ran one of the carbed cars with the hood and air cleaner removed and observed "Old Faithful" after the engine was fully warm - the bowl vents would spew fuel several inches into the air, and that gasoline would fall back into the carb and literally make the engine run so rich that at idle it would choke down and quit...

I tried heat resistant gaskets, heat shield and everything else I and my group of carb-lovers could think of without any respite. The only one we didn't try was to direct the output of the car's air conditioning system at the carb.

Nothing got rid of the problem.

I'm convinced it is not the carb's fault! It is the gasoline which has changed that makes this happen.

That's why I went to EFI - and no more problem. At least not of that kind ;-)

My theory is that the float bowl temps become higher than the "gas" can withstand without vaporizing, the fuel boils in the float bowls, and "thar she blows!"

Good luck!

Tom

PS: One thing that I didn't get to try was the no-alcohol gas. Maybe you could try a tankful or two (if it wouldn't hurt your engine!) and let us know if it changed any of the symptoms?