What are you generally using as oil in your cars? I'm rebuilding 100 000 miles driven engine and it is dirty as hell. Salvaged car was shipped year ago for parts donor. Oil rings and scraper ring groove is full of hard carbon deposit. One compression ring was stuck in groove.
Three cylinders had low compression according to worn valve seats, but all rings was dirty. I cleaned part of scraper ring.



Three cylinders had low compression according to worn valve seats, but all rings was dirty. I cleaned part of scraper ring.


