As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) THE EXHAUST VALVE ROCKER ARM BOSS CRACKED THROUGH THE PIVOT BOLT HOLES WHICH ALLOWED THE ROCKER ARM TO MOVE WITHOUT OPENING THE EXHAUST VALVE, SEVERLY REDUCING ENGINE POWER. FROM DISCUSSIONS WITH SEVERAL AME'S THE CONSENSUS IS THAT OVERTORQUING OF THE PIVOT BOLT, AT SOME TIME IN THE PAST, COULD CAUSE FATIQUE IN THIS AREA. THIS CYLINDER HAS HAD NO REPAIRS SINCE LAST OVERHAUL.