Had the Dart (360/727/8/34) out for a ride and wash today. The carb is a Holley List 80508, 750 cfm, single accelerator pump, dual inlet, vacuum secondary. While heading home I goosed it through 1st and 2nd gears. Let off to cruise and the engine began to stutter. I managed to keep it alive for a little ways by tap dancing with the throttle, but then she dies. I pop the air filter off and attempt to start it and the secondary vent tube is pissing fuel out and the car will not run below 2500 rpm or so. Tried tapping on the float bowl and fiddling with the float adjustment - no luck. Finally disconnected and plugged the fuel inlet to the secondary bowl and drove home on the primary side.

What I don't understand is why the secondary float would suddenly stick like that. I didn't change anything in the fuel delivery system and the ride was smooth and normal until then. For now the car will sit. I guess I'll pull the carb off when it is cooler but I'm not sure what I will be looking for.

Why did this happen? Anybody have any thoughts or advice?