I checked the head torques tonight. With the wrench set to 55 ft-lb, I was able to get some movement on maybe 1/3rd of the nuts. But hot compression test results were exactly the same.
I also did a wet test on the bad cylinders and saw very little difference, a few psi higher. In fact I was surprised by how small the difference was. I squirted 4 good shots of oil towards the back of the cylinder, so I think that should have got to the rings?
After the tests, just out of curiosity, I started the engine again to check timing with a timing light since I had marked TDC on the crank pulley earlier. The light showed only occasional spark on #1, occasional no-spark periods on #2, and steady spark on 3, 4, 5, and 6. The engine ran out of gas before I got to 7 and 8. I got some more gas, and it wouldn't start hot. (This is the first time I have tried to start it hot.)
I'm beginning to think this engine doesn't run as well as reported.
Malcolm
PS: the carrier has a Zenith carb with a governor.