As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A SCHEDULED INSPECTION IT WAS FOUND THAT THE NR 1 CYLINDER HAD LOW COMPRESSION. INVESTIGATION FOUND THE CYLINDER HEAD WAS CRACKED AROUND THE INTAKE VALVE SEAT AND THROUGH THE CYLINDER HEAD WALL OUT BETWEEN THE CYLINDER COOLING FINS.