Since I posted my tach readings above, the compression has gotten a bit softer. I think this engine got a marginal ring from the factory as it loses it's seal quickly as the prop is rotated slowly. My s90 does not exhibit this behavior and it has a factory ST ring. I am going to re-ring the engine and after breaking the new (Bowman) ring in, I will retest the engine and post readings. I have another muffler or two ill test as well. The engine still runs good, but I think a better sealing ring will up the power a bit. In previous tests, I got a lower rpm reading after the engine was up to operating temp

I like the fact that Bowman rings cover the locating pin for the ring where others do not. Results to come.