AN SMA PLT HAD A PARTIAL ENG FAILURE. HE WAS ABLE TO FLY TO HIS DEST.

Narrative

DURING NORMAL CRUISE AT 11000 ON AN IFR FLT FROM OAK; CA; TO SCOTTSDALE; AZ; THE ENG OF MY SMA SUDDENLY STARTED RUNNING ROUGH. THIS OCCURRED 60-70 MI W OF SCOTTSDALE ON V16. I NOTIFIED CTR THAT I HAD A PROB BY DECLARING 'PAN; PAN; PAN.' I DECIDED TO PROCEED TO THE CLOSEST ARPT WHICH WAS 40 MI E ON V16 WHILE ATTEMPTING TO DIAGNOSE THE PROB. MANIFOLD PRESSURE; RPM; FUEL PRESSURE; OIL TEMP; OIL PRESSURE; CYLINDER HEAD TEMP; AND EGT WERE ALL NORMAL (AND UNCHANGED EXCEPT FOR CYLINDER HEAD TEMP; WHICH WAS IN THE LOW GREEN). MAGNETO CHK DID NOT CHANGE ROUGHNESS; NOR DID MIXTURE ADJUSTMENT OR RAM AIR. THE AIRPLANE MAINTAINED ALT EASILY AT 11000; HOWEVER; GND SPD DROPPED 15-20 KTS TO 125 KTS. IN THE NEXT 20 MINS; THERE WERE NO CHANGES IN AIRPLANE PERFORMANCE. BECAUSE BUCKEYE ARPT DID NOT APPEAR TO HAVE A REPAIR FACILITY ACCORDING TO MY COMMERCIAL HANDBOOK AND BECAUSE I BELIEVED THAT I COULD SAFELY COMPLETE THE FLT; I REQUESTED AND RECEIVED FROM ATC 'CLRNC DIRECT' TO SCOTTSDALE. ATC CLRED ME TO LOWER ALT AS I APCHED THE TCA; HOWEVER; I REQUESTED AND RECEIVED CLRNC TO REMAIN AT 11000 UNTIL I HAD VISUAL CONTACT WITH THE FIELD. I LANDED UNEVENTFULLY AND TAXIED TO THE FBO WHERE THE ENG WAS EVALUATED AND REPAIRED. THE EXHAUST VALVE ON CYLINDER #3 HAD CRACKED.