Why does fuel shoot out of the top of a rochester 2 barrel carb?

Possibly the float is stuck or the needle valve is stuck or has dirt in it. Clamp off the fuel line going to the carb so no new fuel can get in. Start the vehicle & run it till it runs out of fuel. By doing this if you're lucky whatever is stuck in the valve may sink to the bottom of the bowl. Unclamp the fuel line after the engine runs out of fuel and restart the engine. Hopefully it will now be o/k and save you having to disassemble the carb. If it still does it, it's time to disassemble and while you're at it you might as well put in a kit.