I fairly recently changed the heads and exhaust on my '87 Westy.  Sometimes
when I start the engine, I hear a thump from the engine compartment. When
the engine "catches" the torque causes the engine to rotate in the engine
compartment.  The exhaust pipe, from the left back cylinder, hits a
structural support bar, under these conditions.  (The exhaust hits where
the pipe makes its 90 degree bend toward the front of the van.) The exhaust
is OEM, and I've tried to adjust it so that there is more clearance (I
suppose there is about .25" clearance). The exhaust system fits so tightly
that there is not much "play".  Has anyone else had this problem? Will I
damage the exhaust (probably) if this continues to be a problem? Any
suggestions would be greatly appreciated.