We have a 90 KW T600 with a 3406B , 4MG 73310. Bought 3 years ago, no history known, has done well for three years. Recently suspected we might have small exhaust manifold leak, so cleaned area well, and began inspecting. Found 3 broken studs, so removed the rest, two more broke then. Got all broken studs out. Checked out manifold and it has a long hairline crack in the web between the two turbo ports, so it's junk.

The head has round ports, the manifold has square ports. I would have thought that when the engine was built new that they would have been the same. Anybody know how to tell what originally was on this engine? I searched old posts and found where tony stated that it is OK to use the square port manifold with a round port head. Was the head originally square port? Is there even a round port manifold available for this engine?

Any input is appreciated. Thanks.