Holley question - Why did my float suddenly stick?

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?

Sunk float or something stuck between the needle and seat.

Thanks guys. If I don't find an obstruction in the needle and seat how do you inspect/test a float?

Take both floats out of the fuel bowls and look at them and feel if one is heavier or lighter than the other one.
If they are brass floats shake them and listen to see if one has fuel in it or not

Thanks Cab.

Shake them too and you can hear/feel if they have gas in them

Do be aware that a microscopic piece of anything is enough to hold the needle off its seat. While you have it apart blow all the lines and passages out with compressed air.
iAnd just an FYI, have had a few occasions where fuel lines that appeared OK on the outside were rusty on the inside. That'll lead to some frustration

The shake test doesn't always work. Especially if a carb has been sitting.

To test a brass float, boil a pot of water, remove from stove and let it sit a few minutes so there are no bubbles floating around. While the water is still hot use pliers to completely submerge the float. If there is a hole you'll see bubbles coming from it just like checking a tire for leaks. The hot water is causing the air inside the float to expand, forcing it out of any pinholes in the solder seam. Won't create enough pressure to pop a good float.

If the carb uses the black solid plastic floats, replace them with brass units, I've had a few of the black plastic Holley floats "absorb" gasoline, once they do, there's no remedy, but a brass replacement....do check the needle/seat assy as mentioned as that's another source of flooding/no bowl filling situations on Holleys

Mike

Can you say ETHANOL ?