[nkaminar]

Some engines and manifolds do not have the counterbores that the exhaust rings fit into. You should be able to hear an exhaust leak. Partially block the exhaust pipe with a potato to better hear and see the exhaust leaks. Exhaust leaks can be dangerous to your health so look at that first. Lots of exhaust getting into the intake can make the car run bad. You should be able to see black soot at any exhaust leaks.

If the carburetor is leaking lots of gasoline then that could be your issue. Hate to suggest this but you may want to take the carburetor apart again and check for a non-leaking float valve. You should be able to turn the carburetor up side down and not be able to blow or suck anything from the gasoline inlet. Gasoline is toxic so make sure the passage are clean before doing any sucking. It could be that the valve needs tightening or that there is flaw where it screws into the carburetor body that will make the gasket not seat correctly.