As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED SMOKE IN THE COCKPIT AFTER LANDING. AFTER AN INSPECTION OF THE ENGINE, IT WAS FOUND THAT NR4 CYLINDER HEAD OIL RETURN LINE "B" NUT HAD BACKED OFF CAUSING OIL TO DRIP ONTO THE EXHAUST STACK WHICH CAUSED THE SMOKE IN THE COCKPIT. THE MECHANIC INSTALLED AND TIGHTENED THE LOOSE "B" NUT AND INSPECTED ALL OTHER CYLINDERS FOR ANY OTHER LOOSE "B" NUTS. NO OTHER LOOSE OIL RETURN "B" NUTS WERE FOUND TO BE LOOSE. THE ACFT WAS RETURNED TO SERVICE AND THE PROPER PAPERWORK WAS COMPLETED.