As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, PILOT/OWNER HAD A LOSS OF POWER AND ENGINE RAN ROUGH. PILOT RETURNED TO AIRPORT WITH ENGINE PRODUCING REDUCED POWER. UPON INSPECTION MAINTENANCE FOUND THE INTAKE VALVE SEAT HAD COME LOOSE FROM CYLINDER. THE ENGINE HAD RECENTLY HAD A TOP OVERHAUL 112 HOURS EARLIER WITH NEW CONTINENTAL CYLINDERS.