As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT IN FLIGHT NOTICED ENGINE RPM TO DROP SIGNIFICANTLY AND THE ENGINE RUNNING ROUGH. PERFORMED INSPECTION OF ENGINE AND NOTED CYLINDER VALVES NOT ACTUATING. REMOVED ENGINE SUMP AND FOUND PORTION OF CAMSHAFT IDLER GEAR IN SUMP. REMOVED ACCESSORY HOUSING AND FOUND CAMSHAFT IDLER GEAR BENT AND SECTION HAD BROKEN OFF.