As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A ROUTINE INSPECTION, SEVERAL CRACKS WERE SEEN AT THE LOWER SPARK PLUG HOLE OF THE NR 1 CYLINDER. AFTER THE CYLINDER WAS REMOVED, NUMEROUS CRACKS COULD BE SEEN IN THE INSIDE OF CYLINDER HEAD TO EITHER SIDE OF THE LOWER SPARK PLUG HOLE. THE CYLINDER SHOWED NO INDICATION OF DISCOLORING OR ANYTHING THAT WOULD INDICATE IT WAS EXPOSED TO EXTREME HEAT.