[57taskforce]

Good advice! I build natural gas compression engines for a living, anything from nat gas turbo 5.9 Cummins to turbo 3306 cats, hell we even have some dinosaur wakeshas laying around I’ve been thru. I more or less do what ho455 stated above. I usually let it get a little heat for a minute or two on the test stand while I make sure the timing is right and I don’t have any leaks or anything else bad going on. then it’s straight to higher rpm pulls in succession as stated above. One thing I’ve had good luck with is trying to keep engine heat between 210-230*. I’ve found that the heat seems to help seat the rings a little better. In looking at your back three cylinders something clearly is a miss.I doubt it’s your rings. To me the piston tops and cylinders look way to clean to have weak rings there’s no burnt oil or carbon deposits. Other than the little bit of carbon on the heads it looks to me like it’s not getting any/enough fuel. Those compressions numbers while weak should be enough for it to run. you say your valves don’t look like they are sitting in the seats right. What was done to the head when you had it rebuilt? Was it a full on rebuild? Im interested to see what your machinist finds when he looks it over. I’m thinking your loosing compression thru the valves.