As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING STANDARD 50 HOUR SCHEDULED OIL CHANGE AS S.O.P. DIFFERENTIAL CYLINDER LEAK CHECKS ARE PERFORMED. CYLINDER #1 WAS 60/80 PSI, OTHER CYLINDERS WERE IN MID TO UPPER 70'S. ENGINE HAD LEAKING EXHAUST VALVE. ENGINE TIME SINCE OVERHAUL: 1271.8 HOURS.