I think I found the reason for the over heating I wrote about some time
 ago. I appears to have been the result of my own ignorance. It appeared
 to me that the reason for the local overheating must be somewhere in the
 coolant flow. I think, one of the responders to my previous report
 mentioned 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.

 Richard Sohn
 N2071U

 Randy, You need to check yours for this.

 Paul Lamar


Hi Richard;
I don't think I mentioned this before.  The area around the plugs can
expand into the housing with uneven or extreme overheat events.
I've typically only heard of this with overheated 400HP+ turbo
installations.
Have you checked the apex seal path for permanent set?
Here are a few old threads some folks might be interesting:
 http://www.rx7club.com/forum/showthread.php?t=751977
 http://www.rx7club.com/forum/showthread.php?t=936073&page=2
 (I personally like the rotary fountain;)
Anything approaching cooling fins such as will provide more surface area
for heat transfer.
Cheers
Cary

The bottom line is install a "cylinder head" temperature thermal
couple if you suspect problem. Anything under 500 F is no reason
for concern if you are mixing two cycle oil.

In 12 years we have not seen these problems at aircraft power levels.
At 400 HP you would be burning something like 38 gallons
an hour. An RV4 would fly for less than 50 minutes at that rate :)
No reserve!

Reno racing could be another matter.

Paul Lamar