What was found
DURING CLIMB OUT OF STT THE CREW REPORTED A DECREASE RT ENGINE MANIFOLD PRESSURE. SUBSEQUENT INCREASE IN RT THROTTLE LEVER DID NOT INCREASE MANIFOLD PRESSURE THOUGH MANIFOLD PRESSURE STABILIZED AT 26". THE FLIGHT WAS CONTINUED. RT ENGINE OIL TEMPERATURE BEGAN TO REDLINE AND OIL PRESSURE DROPPED DURING APPROACH ACCOMPANIED BY A VIBRATION FROM THE RT NACELLE. THE ENGINE WAS NOT INTENTIONALLY SHUTDOWN AND THE PROPELLER DID NOT ENTER A FEATHER CONDITION DUE TO LACK OF OIL PRESSURE. THE FLIGHT LANDED SAFELY AT THE INTENDED DESTINATION. SUBSEQUENT INSPECTION REVEALED THE NR 3 CYLINDER AND PISTON ASSEMBLY WERE SEVERELY DAMAGED. THE PISTON WAS COMING APART IN PIECES AND THE CYLINDER WALLS WERE SUBSTANTIALLY DAMAGED. THE INTAKE AND EXHAUST VALVES DID NOT EXHIBIT SIGNS OF DAMAGE. THE DAMAGE APPEARS TO HAVE BEEN CAUSED BY A PRE-IGNITION EVENT IN THE NR 3 CYLINDER. THIS ENGINE WILL BE REMOVED FROM SERVICE FOR OVERHAUL AND THE AIRFRAME SHOWER OF SPARKS SYSTEM WILL BE FUNCTIONALLY TESTED AND INSPECTED PRIOR TO FURTHER SERVICE.