It appeared to me
that the reason for the local overheating must be
somewhere in the coolant flow. I think, someone on the
other e-mail group pointed to that possibility.
What it boils down to
is the fact that not all the cooling pockets in the
rotor housing are open to coolant flow. In particular,
the second opening on the inlet side is totally blocked
off by the side housings. I left it open, and worsening
the situation, there is a comparatively large hole in
the rotor housing web. As a result, most of the coolant
did go through this opening, and not through the area
around the plugs. If I had looked close at the flow
pattern from MAZDA this problem could have been avoided.
Fortunately, there is
no permanent damage to the engine, and the engine in the
airplane has not run yet. I fixed the problem by closing
off the opening. The engine is now going back to the
test stand for another 10+ hrs of beating.