As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE STARTED TO RUN ROUGH WITH POWER LOSS ON TAKEOFF CLIMB. RETURNED TO AIRPORT AND LANDED SAFELY. UPPER VALVE SPRING RETAINER BROKE APART WHICH ALLOWED EXHAUST VALVE TO DROP INTO CYLINDER COMBUSTION CHAMBER ON A NEW CYLINDER WITH 8.0 HOURS ON IT. EXHAUST VALVE HEAD WAS BROKEN INTO MULTIPLE PIECES WITH THE MAIN SECTION LODGED INTO PISTON HEAD. EXHAUST VALVE STEM WAS FOUND IN EXHAUST SIDE OF TURBO IMPELLERS. METAL FOUND IN OIL FILTER. CYLINDER COMBUSTION CHAMBER AND PISTON DAMAGED.