As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE CHANGING VALVE COVER GASKET ON NR 3 CYLINDER, MECHANIC FOUND TWO SMALL PIECES OF METAL IN VALVE COVER. INVESTIGATED AND DETERMINED PIECES CAME FROM THE EXHAUST VALVE INNER VALVE SPRING RETAINER TCM. PERFORMED HIDDEN DAMAGE INSPECTION. INSPECTED AND CHECKED OK. INSTALLED NEW SPRING RETAINER. ENGINE IS A TCM FACTORY REMANUFACTURED WITH 1,336 HOURS TSMOH.