What was found
PILOT REPORTED LOSS OF RPM, ENGINE ROUGHNESS IN CRUISE FLIGHT, CONFIRMED BY EXTREMELY HOT INDICATION ON AIRCRAFT EGT SCANNER. NR 6 CYLINDER POSITION, FOUND NR 6 CYLINDER EXHAUST VALVE BURNED THROUGH, SEAT DETERIORATED BEYOND LIMITS. REMOVED NR 4 CYLINDER TO FACILITATE REMOVAL OF NR 6 CYLINDER. FOUND EXHAUST GUIDE WORN BEYOND LIMITS ON NR 4 CYLINDER. INSTALLED NEW FACTORY SUPPLIED CYLINDER NR 6 POSITION AND REWORKED AND INSTALLED NEW GUIDE NR 4 CYLINDER. ENGINE TEST RUN AND FLOWN.