Cummins Big Cam III engine failures

I made a half repair to a Cummins Big Cam III engine, I am well accentuated, without smoke, with good oil pressure and without closing, work well two days after accenting it but on the third day I was working normally and suddenly it began to lose power and made a lot of human breathing and it kicked. What can be the cause? I appreciate your answers beforehand. thank you

You know if they didn't warm it. Did you already check it, you are not compression?