As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT IN CRUISE FLIGHT AT 2200 FT, ENGINE BEGAN TO RUN ROUGH. PILOT DECLARED AND EMERGENCY AND LANDED AT AIRPORT. AFTER LANDING THE VALVE COVER WAS REMOVED FROM THE NR 2 CYLINDER AND IT WAS DISCOVERED THAT ALL 3 BOSSES FOR THE VALVE ROCKER SHAFTS HAD BROKEN. (K)