As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE INBOUND FOR LANDING, ENGINE BEGAN TO RUN ROUGH. PILOT LANDED SAFELY. MECHANIC REMOVED SPARK PLUGS. FOUND NR 2 CYLINDER PLUGS OILY. REMOVED ROCKER COVER TO FIND INTAKE ROCKER BROKEN. VALVE STEM REVEALED GALLING AND SHARP EDGES ON STEM. INTAKE VALVE COVERS ON OTHER VALVES TO REVEAL THE SAME. EXHAUST VALVES OK. SUBMITTER STATED WRONG KEEPERS WERE USED.