As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT LANDED AFTER IN FLIGHT ENGINE VIBRATION. THERE WAS OIL ON THE WIND SCREEN. INSPECTION REVEALED THE #1 CYLINDER WAS LOOSE ON THE CRANKCASE, EIGHT CYLINDER HOLDDOWN STUDS WERE FOUND SHEARED FLUSH WITH THE FLANGE THE REMAINING TWO STUDS WERE FOUND LOOSE.