As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NR 2 EXHAUST VALVES SEIZED IN VALVE GUIDE AND VALVE HEAD SEPARATED AFTER CONTACT WITH PISTON. SEIZURE OF VALVE STEM IN GUIDE MOST LIKELY DUE TO CARBON ACCUMULATION. AIRCRAFT OPERATED UNDER 14CFR PART 141. SUBMITTER RECOMMENDATION: C/W SB 388B AT MORE FREQUENT INTERVALS.