What was found
ON A SHORT FLIGHT, A ROUGHNESS DEVELOPED IN THE LEFT ENGINE. NO EMERGENCY ACTION WAS REQUIRED. AFTER PERFORMING A COMPRESSION CHECK, FOUND THE EXHAUST VALVE SEAT ON NR 2 CYLINDER HAD BECOME DISLODGED CAUSING THE EXHAUST VALVE TO REMAIN PARTIALLY OPEN. THE CYLINDER (HEAD) IN THE AREA OF THE EXHAUST SEAT WAS DAMAGED BEYOND REPAIR, AND THE VALVE OR SEAT CAUSED MINOR DAMAGE TO THE PISTON. NO CAUSE FOR THE SEAT BECOMING DISLODGED HAS BEEN DETERMINED.