What was found
(CAN) DURING THE PREFLIGHT GROUND RUN THE PILOT NOTICED AN ENGINE VIBRATION. THE ACFT WAS SNAGGED AND INSPECTED BY MAINTENANCE. 6 OUT OF 8 STUDS ON THE NR 3 CYLINDER WERE SHEARED OFF. ALL THE STUDS WERE REPLACED. ALL 4 CYLINDERS BASE NUTS WERE CHECKED FOR PROPER TORQUE. THE ENGINE WAS ON CONDITION AT THE TIME. THE CYLINDER HAS NEVER BEEN REMOVED SINCE O/H. TWO OTHER CYLINDERS WERE REMOVED FOR THE ENGINE ON CONDITION IMPLEMENTATION AT 2065 HRS. THE ENGINE RECIEVED ON CONDITION INSPECTIONS EACH 50 HRS THEREAFTER. THE ACFT HAS RECEIVED TWO INSPECTIONS SINCE THE OCCURANCE, AND NO FURTHER DEFECTS HAVE BEEN FOUND.