As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED THAT AFTER AN HOUR AN HALF IN CRUISE FLIGHT THAT THE LEFT ENGINE EGT HAD FALLEN BELOW AN OPTIMUM LEVEL FOR CRUISE FLIGHT. TRIED TO ADJUST THE LEFT ENGINE FUEL FLOW WHICH GAVE NO SIGNIFICANT CHANGES FOR OPTIMUM FUEL ECONOMY. THE PILOT ALSO NOTED THAT THE ENGINE HAD NO NOTICEABLE CHANGE IN PERFORMANCE AND DID NOT EXECUTE ANY PRECAUTIONARY MANEUVERS. UPON ARRIVAL TO RDU PILOT REPORTED THE ANOMALY TO MAINTENANCE. MAINTENANCE INVESTIGATED THE REPORT AND FOUND THE NUMBER ONE CYLINDER HEAD CRACKED ON THE LEFT ENGINE. MAINTENANCE REMOVED ENGINE FROM SERVICE FOR ANALYSES.