Paul,
At last, my single rotor is running!  It starts easily, idles smoothly--if 2800 rpm qualifies as "idle."
Today, after completing the long list of adjustments needed from the last short test run, the engine performed as expected.  No geysers of oil, no long stream of radiator fluid on the ground--no leaks at all, in fact.  I ran the RPM up to 5000 for a short while, letting the water temps rise to 154 degrees, 127 on the oil.  When throttled back to 3000 rpm, the temps cooled back down a bit and remained stable at 150/120.  First time I've seen that.  Previously, the temps were a function of time, the longer the engine runs, the hotter it went.

It did well today, running for about 1/2 an hour.

Still have to build a cowl, and optimize the temperatures, but I wanted to say thanks for your help.  You offered good advice.

Lewis.

Looking good Lewis.  If the cowl is done right it will cool.
Put some louvers on the left side of the cowl.
The wedge diffuser will then shield the rad from engine heat.
A one degree increase in cooling air temp will reduce the
cooling 1%.

Paul Lamar