As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED THAT IN CRUISE FLIGHT, THE ENGINE BEGAN RUNNING ROUGH. IT WAS FOUND THE NR 1 CYLINDER HAD ZERO COMPRESSION. WHEN THE EXHAUST VALVE WAS REMOVED FROM THE ENGINE, DISCOVERED THE VALVE HAD A MISSING CHUNK. SUSPECT CAUSE - CARBON BETWEEN VALVE AND SEAT CAUSING RAW FUEL TO PASS BY THE VALVE AND BURN THE VALVE WHEN IGNITED. .25 INCH BY .25 INCH GONE FROM VALVE TOP.