As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING FLIGHT ENGINE DEVELOPED UNUSUAL DRONING NOISE FROM ENGINE. SUSPECT WORN CAM LOBE. CAM REMOVED AND FOUND TO BE WORN ON SEVERAL EXHAUST CAM LOBES. SERVICEABLE CAM, ROLLERS AND PINS INSTALLED. ENGINE GROUND RUN SATISFACTORY. AIRCRAFT RELEASED. SATISFACTORY FLIGHT TEST CONDUCTED.