Every one of these I've ever seen (please go back to 1964 as a starting point) is a pipe thread situation...meaning the further you screw it in, the tighter it gets. Now for the disclaimer: I have seen a handful of these (maybe 6 or so) where the fitting screwed all the way in. On those, leaks were common. The pipe thread will stop leaks by design. Why did these half dozen or so screw in all the way? I can't unscramble that egg because I didn't mess them up but every one of them leaked in some fashion...meaning some leaked very notably and others dribbled so that after a while the whole side of the carburetor would be covered in gas. How to know if yours is leaking here or elsewhere? Detective work 101...cut a strip of old t-shirt or other fabric about 1/4 inch wide by around 8 or so inches long, wrap it around the fitting where it attaches to the carburetor air horn (but not where it will touch the dividing line between the air horn and the float bowl), tie it in a knot and idle or drive for a while. If it is notably wet, your leak is there. If it remains dry but the gasket/dividing line between the air horn and the float bowl is wet then your leak is there and you have another problem. If that dividing line gets wet while you're idling it is very likely your float/needle/seat isn't working correctly or (maybe and/or) you have way too much pressure from your fuel pump and you're pushing so hard against the needle/seat that it can't hold back the input. Something like that. Let's first find out where the leak is...
