Narrative:

We departed dallas north airport at XA30 on 7/wed/88 with 52 gals of 100 ll fuel (6.5 hours) for the 4.5 hour flight to stl. Cruise altitude was 7500' MSL. Three hours after takeoff the engine began running extremely rough. I declared an emergency by calling the sgf tower. Tower had me contact sgf approach. I was assigned a transponder code and given clearance for a straight in approach to runway 19. We landed safely at sgf. No one was injured and no damage was sustained to the aircraft. Inspection of the engine revealed metal fragments in all 4 cylinders and the oil screen. The mechanic believes that an intake valve failed. The engine must be replaced. From talking with other mechanics, I feel that this type of engine failure could have been prevented if the mechanic who performed my annuals had questioned the low compression on the #4 cylinder.

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Original NASA ASRS Text

Title: GA SMA PARTIAL ENGINE FAILURE. EMERGENCY LNDG AT NEARBY ARPT.

Narrative: WE DEPARTED DALLAS NORTH ARPT AT XA30 ON 7/WED/88 WITH 52 GALS OF 100 LL FUEL (6.5 HRS) FOR THE 4.5 HR FLT TO STL. CRUISE ALT WAS 7500' MSL. THREE HRS AFTER TKOF THE ENG BEGAN RUNNING EXTREMELY ROUGH. I DECLARED AN EMER BY CALLING THE SGF TWR. TWR HAD ME CONTACT SGF APCH. I WAS ASSIGNED A TRANSPONDER CODE AND GIVEN CLRNC FOR A STRAIGHT IN APCH TO RWY 19. WE LANDED SAFELY AT SGF. NO ONE WAS INJURED AND NO DAMAGE WAS SUSTAINED TO THE ACFT. INSPECTION OF THE ENG REVEALED METAL FRAGMENTS IN ALL 4 CYLINDERS AND THE OIL SCREEN. THE MECH BELIEVES THAT AN INTAKE VALVE FAILED. THE ENG MUST BE REPLACED. FROM TALKING WITH OTHER MECHS, I FEEL THAT THIS TYPE OF ENG FAILURE COULD HAVE BEEN PREVENTED IF THE MECH WHO PERFORMED MY ANNUALS HAD QUESTIONED THE LOW COMPRESSION ON THE #4 CYLINDER.

Data retrieved from NASA's ASRS site as of August 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.