As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE EN ROUTE, LEFT ENGINE STARTED TO RUN ROUGH. PILOT FEATHERED PROPELLER AND SECURED ENGINE. AN UNEVENTFUL LANDING WAS MADE. MAINTENANCE FOUND NR 1 CYLINDER CRACKED. CYLINDER REPLACED WITH AN OVERHAULED UNIT. ENGINE GROUND RUN AND RETURNED TO SERVICE. (X)