Welcome to the forum.
Pretty sure this is a common problem on the 8N
First thing I'd suggest is to tap on the side of the carb with the butt of a screwdriver or similar to see if whatever is stuck gets freed up.
Instead of typing out the possibilities, I'm going to suggest you do an internet search for "8N Ford carburetor overflows".
It's normally one of just a few minor things related to stuck or flooded float, needle not seated or other.