Every carburetor I have even seen or rebuilt (which has been hundreds) have got an atmospheric vent for the float bowl, if it did not, the gas could not be drawn out through any of the jets by vacuum.
However, external flooding on these carbs is common. Over choking, excessive fuel pressure, defective float/float valve & seat and in some cases to small diameter of fuel line from the pump to the carb can cause this issue. Question first is? Is it really boiling (from temperature) or being forced out by a pressure issue? Fuel pump pressure and volume test at the carb inlet would be a good test to start with.
