Likely,the gas stunk really bad, and owner was revving the **** out of it in hopes it would clean up. Did just the opposite i guess.Burned valve?
I pulled a few plugs and was doing compression tests and found the dead one. Thats as far as i go.well i did pull valve cover and valves are moving.
I know he wont want me to open it up,so it gets sold as barely running,moving and brakes work.