BEECHCRAFT DUKE A60 PLT HEARS LOUD BANG FROM L ENG FOLLOWED BY LOSS OF PWR. ENG SHUT DOWN. EMER DECLARED.

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DEPARTED TRI; CLBED UP TO 5500 FT MSL DIRECT HMV; HOLSTON MOUNTAIN VOR. INTERCEPTED A RADIAL S BY SE TOWARDS 5A7 (BANNER ELK; NC). DSNDED TO 4300 FT MSL FOR APCH INTO 5A7. DSNDED IN VALLEY WITH MOUNTAIN PEAKS TO EITHER SIDE OF AIRPLANE. PLT VISUALLY MAINTAINING SEPARATION WITH MOUNTAINS. PLT HEARD LOUD BANG FROM L ENG COWLING/NACELLE. PLT IMMEDIATELY FELT L ENG LOSE PWR; BUT NOT COMPLETELY. PLT CORRECTED ACFT BY BANKING 5 DEGS INTO R SIDE AND APPLYING R RUDDER. PLT CONFIRMED L ENG HAD A PROB. PLT NOTICED L MANIFOLD PRESSURE DECREASING FROM 25 INCHES TOWARDS THE 15 INCH MARK. ALSO L OIL PRESSURE WAS DECREASING FROM A HALFWAY POINT OF: BOTTOM OF GREEN ARC AND ZERO INDICATION. PLT IMMEDIATELY PULLED L THROTTLE TO IDLE; FEATHERED L ENG; AND PULLED L MIXTURE TO IDLE CUT OFF. AFTER SECURING ACFT FOR SAFE FLT; PLT RADIOED TO ZME ON THE SIT. PLT DECLARED AN EMER AND ACCEPTED IMMEDIATE RWY CLRNC TO LAND AT TRI APPROX 15-20 NM AWAY. PLT PROCEEDED DIRECT TRI WITH GPS AND LANDED WITHOUT INCIDENT ON RWY 5 AT TRI. UPON ENG TEARDOWN IT WAS DISCOVERED THAT THE CAMSHAFT LOBE OF THE LYCOMING TIO-541-EIC4 WAS THE CAUSE OF EVENTS. THE LOBE HAD DISINTEGRATED AND SPREAD METAL THROUGHOUT THE ENG CAUSING THE CONNECTING ROD OF #6 CYLINDER TO THROW A CAP. THE CONNECTING ROD PROCEEDED TO VENTILATE THE CASE IN SEVERAL AREAS. THIS WAS THE LOUD BANG AND SUBSEQUENT LOSS OF PWR. THE TBO OF THE TIO-541- EIC4 ENG IS RATED AT 1600 HRS. THE RECORDED TIME ON THE L ENG WAS: 1136.1 HRS WITH 463.9 HRS REMAINING. THE R ENG ALSO WAS REBUILT DUE TO THE CAMSHAFT FAILING. THE REASON: '#4 EXHAUST VALVE CAM-LOBE WAS WORN BEYOND LIMITS.' THE PLT FEELS THAT THESE CAM SHAFTS ARE NOT UP TO THE EXPECTATIONS OF THE ENG'S TBO. PERHAPS SOMETHING TO LOOK INTO FURTHER. OVERALL; THE PLT HANDLED THE SIT WITHOUT ANY FURTHER INCIDENCE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THE OWNER CONTACTED LYCOMING WITH A PROMISE THAT THEY WOULD SEND A REPRESENTATIVE TO INSPECT THE ENG. NOTHING HAS OCCURRED SINCE THAT TIME; NO CONTACT WHATSOEVER. THE OWNER HAS RETAINED AN ATTORNEY AND WILL PROCEED FURTHER. RPTR IS A MEMBER OF A DUKE OWNERS' ORGANIZATION AND HAS SPOKEN WITH SEVERAL OTHER MEMBERS WHO HAVE HAD SIMILAR PROBS. MOST ALL OF PERSONS HE SPOKE TO HAVE HAD FAILURES BEFORE THE TBO FOR THAT ENG. THE CAMSHAFT IS PARTICULAR TO THE DUKE ACFT AND WAS USED ALSO ON THE BARON 56 TC WITH DUKE ENGS. THE CAM LOBE IS AN EGG SHAPED UNIT OF WHICH THERE ARE TWO PER CYLINDER. THEY ASSIST WITH OPENING AND CLOSING OF THE VALVES. THE MECH RPTR SPOKE TO INDICATES HE FEELS THAT METALLURGICALLY THE LOBE IS NOT UP TO THE STANDARD FOR PROJECTED ENG LIFE. SINCE THERE WERE 596 DUKES MADE THERE ARE TWO TIMES THAT MANY OPPORTUNITIES FOR MORE PROBS. SOMEONE SHOULD DO FOLLOWUP SINCE LYCOMING DOES NOT SEEM TO BE INTERESTED.