As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APPROXIMATELY 12 TO 15 MILES FROM AIRPORT, ENGINE BEGAN TO RUN ROUGH. THE TOWER WAS ADVISED AND THE ACFT WAS CLEARED FOR A STRAIGHT IN LANDING. TAXIED TO RAMP WITHOUT INCIDENT. TROUBLESHOOT ROUGH RUNNING ENGINE AND FOUND NO COMPRESSION ON NR 6 CYLINDER, REMOVED CYLINDER AND FOUND EXHAUST VALVE BURNED. ALSO, REMOVED NR 1 AND NR 4 CYLINDERS DUE TO LOW COMPRESSION. THE ENGINE HAS NEVER BEEN O/H SINCE NEW AND HAS 1640 TOTAL HOURS.