Narrative:

Small aircraft was flying at 7000' MSL on top of a solid layer of clouds, with 2 people on board: student and instrument. We had just departed mie and were tracking directly to the olk VOR. All of a sudden (west/O any prior indication) the engine started to shake and we noticed a power loss. We slowed the aircraft down in order to save some valuable time and asked ft wayne approach control for a vector to the nearest airport (marion, in). They gave us a heading of 210 degrees and we started a shallow turn to the left to a heading of 210 degrees. By that time we were in IMC. The student flew the aircraft, while I did my checklist to get the engine to operate properly. As nothing seemed to work and the shaking got rougher, we decided to shut down the engine. We noticed a 700 FPM descent, while maintain airspeed and 210 degrees on the heading. After breaking out of the clouds at 2500' MSL, we spotted the airport in a matter of seconds. We headed straight for it and made a regular power off landing on runway 22 (we were not too concerned about the favorable runway). After we landed, we contacted grissom approach control to let them know we landed safely at marion, in. We were handed off to grissom right after we got our heading of 210 degrees. It was with grissom that we declared an emergency, stating that we, 'definitely had a problem with our engine.' as we were already in radar contact with ATC we did not think it was necessary to squawk 7700. After a couple of days, when the mechanics had checked the engine, they found a piece of an exhaust valve in the carburetor. They concluded, that the engine had swallowed an exhaust valve, which had come apart because of fatigue. Tach time on the engine was 1999.6 tbo on engine was 2000 hours.

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Original NASA ASRS Text

Title: SMA ON IFR TRAINING FLT HAS ROUGH ENGINE. ENGINE SHUT DOWN, EMERGENCY LNDG.

Narrative: SMA WAS FLYING AT 7000' MSL ON TOP OF A SOLID LAYER OF CLOUDS, WITH 2 PEOPLE ON BOARD: STUDENT AND INSTR. WE HAD JUST DEPARTED MIE AND WERE TRACKING DIRECTLY TO THE OLK VOR. ALL OF A SUDDEN (W/O ANY PRIOR INDICATION) THE ENG STARTED TO SHAKE AND WE NOTICED A PWR LOSS. WE SLOWED THE ACFT DOWN IN ORDER TO SAVE SOME VALUABLE TIME AND ASKED FT WAYNE APCH CTL FOR A VECTOR TO THE NEAREST ARPT (MARION, IN). THEY GAVE US A HDG OF 210 DEGS AND WE STARTED A SHALLOW TURN TO THE LEFT TO A HDG OF 210 DEGS. BY THAT TIME WE WERE IN IMC. THE STUDENT FLEW THE ACFT, WHILE I DID MY CHKLIST TO GET THE ENG TO OPERATE PROPERLY. AS NOTHING SEEMED TO WORK AND THE SHAKING GOT ROUGHER, WE DECIDED TO SHUT DOWN THE ENG. WE NOTICED A 700 FPM DSNT, WHILE MAINTAIN AIRSPD AND 210 DEGS ON THE HDG. AFTER BREAKING OUT OF THE CLOUDS AT 2500' MSL, WE SPOTTED THE ARPT IN A MATTER OF SECS. WE HEADED STRAIGHT FOR IT AND MADE A REGULAR PWR OFF LNDG ON RWY 22 (WE WERE NOT TOO CONCERNED ABOUT THE FAVORABLE RWY). AFTER WE LANDED, WE CONTACTED GRISSOM APCH CTL TO LET THEM KNOW WE LANDED SAFELY AT MARION, IN. WE WERE HANDED OFF TO GRISSOM RIGHT AFTER WE GOT OUR HDG OF 210 DEGS. IT WAS WITH GRISSOM THAT WE DECLARED AN EMER, STATING THAT WE, 'DEFINITELY HAD A PROB WITH OUR ENG.' AS WE WERE ALREADY IN RADAR CONTACT WITH ATC WE DID NOT THINK IT WAS NECESSARY TO SQUAWK 7700. AFTER A COUPLE OF DAYS, WHEN THE MECHS HAD CHKED THE ENG, THEY FOUND A PIECE OF AN EXHAUST VALVE IN THE CARB. THEY CONCLUDED, THAT THE ENG HAD SWALLOWED AN EXHAUST VALVE, WHICH HAD COME APART BECAUSE OF FATIGUE. TACH TIME ON THE ENG WAS 1999.6 TBO ON ENG WAS 2000 HRS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.