As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING EXAMINATION OF ENGINE CORE FOR OVERHAUL, THE NR 5 CYLINDER EXHAUST VALVE ROTOCOIL WAS FOUND TO BE FRACTURED. THE TOP CIRCUMFERENCE OF THE ROTOCOIL STRUCTURE HAD FRACTURED FROM THE ROTOCOIL ASSEMBLY AND REMAINED CAPTURED BY THE EXHAUST ROCKER ARM WHERE IT EXPERIENCED WEAR AND CONTACT WITH THE ROCKER ARM, ROCKER SHAFT BOSS AND ROCKER COVER.