As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT REPORTED HEARING A BANG DURING CLIMB, FOLLOWING BY PARTIAL POWER LOSS AND VIBRATION WAS FELT. AN EMERGENCY WAS DECLARED AND AIRCRAFT RETURN FOR AN UNEVENTFUL LANDING. INITIAL INVESTIGATION REVEALED NR 3 CYLINDER HAS A VALVE HEAD SEPARATED AND IS STICKING OUT OF BOTTOM SPARK PLUG HOLE AREA. FURTHER DETAIL WILL BE SUBMITTED UPON ENGINE TEARDOWN.