As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION FOUND THE NITRALOY GUIDES WORE THE EX VALVE STEMS LEAVING STEPS IN THE STEM AT THE ENDS OF TRAVEL IN THE GUIDE. ONE VALVE HAD .070 INCH WEAR. SUBMITTER STATED CONTINENTAL SHOULD ISSUE A BULLETIN OR SERVICE LETTER ALERTING MECHANICS OF THIS PROBLEM.