[Bob Bidonde]

The design of the manifold to muffler assembly joint allows for some movement, but not much. It is a semi-ball type joint. The muffler assembly develops a lever bending action on the joint, so it needs to be somewhat flexible and allow some rotational movement of the muffler assembly to dissipate the lever action.
Unfortunately, the design lacks a seal, so we have a habit of over tightening the joint. When the joint prohibits movement, the lever action causes the manifold to bend downward and eventually crack between cylinders 3 & 4.