Engine starts then floods

How do you know it is flooding?
Is the tail pipe blowing out raw gas, black smoke?
Does gas leak around the throttle shaft and/or base gasket?
Can you see gas dripping down inside the bore?
If down the, something is preventing the float needle from resting on the seat, allowing gas to constantly overflow the float bowl.
This can be caused by too much fuel pressure, so if this is the symptom, check the fuel pressure. Rule of thumb is 5-7 psi, but I heard some Holley carburetor's might flood if over 5 psi.
What brand name and model number of the carburetor do you have?

You might want to try adjusting the floats. I know you have to be careful when turning the screwdriver to loosen the float bolts because there is a gasket there, so I will get the instructions because it is important because if it is not done right after adjusting the float levels, it will leak gas from that bolt gasket.
I will be right back.
Here it is.