according to the dutra document there are 3 types one most of us see is the full side wall pocket that's cast into the manifold. another one the choke pocket has a section cut out of the cast wall to work with the later style choke,it still was a cast cup. not open to the exhaust. and the 3rd kind that had a hole that was cast into it for the choke pocked and had a stamped steel cup to seal it. that might be his problem with the steel cup leaking