What was found
BIL - PILOT REPORTED A LOSS OF MANIFOLD PRESSURE ON THE LT ENGINE IN CRUISE AND OIL LEAKING FROM LT ENGINE AFTER SHUT DOWN IN BILLINGS. AIRCRAFT LANDED WITHOUT INCIDENT, NO EMERGENCY DECLARED. LEFT ENGINE, NR 2 CYLINDER EXHAUST VALVE FAILED, DAMAGE CAUSED TO CYLINDER, PISTON AND CYLINDER SUBASSEMBLIES. ALL DAMAGED COMPONENTS WILL BE REPLACED WITH SERVICEABLE COMPONENTS AND OPERATIONALLY CHECKED.