As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
VALVE WAS REMOVED BECAUSE UNABLE TO READ S/N WHILE INSTALLED ON ENGINE. ONCE VALVE REMOVED, NUT WAS CHECKED FOR LOOSENESS AND FOUND VERY LOOSE. THIS VALVE, ACCORDING TO LYCOMING SB 518C, IS NOT EVER SUPPOSED TO BE APPLICABLE. LYCOMING WAS NOTIFIED OF THIS FINDING.