As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT REPORTED AN OIL LEAK FROM THE RT ENGINE. MAINTENANCE FOUND A HOLE IN THE ROCKER COVER FOR THE NR 4 CYLINDER. FURTHER INSPECTION FOUND THAT THE EXHAUST VALVE WAS MISSING A KEEPER THAT WAS FOUND IN THE DRAIN FOR THE CYLINDER. THE VALVE CAP WAS ADRIFT IN THE CYLINDER HEAD AND APPEARED TO HAVE BEEN THE CAUSE OF THE PUNCTURE IN THE ROCKER COVER. THE CYLINDER, ROCKER ARM, VALVE CAP AND ROCKER COVER WERE REPLACED. NO REASON FOR THE FAILURE COULD BE FOUND.