Main bearing

1. Set main bearings in their proper positions on cylinder block and main bearing cap.
2. Install main bearing cap to cylinder block.

   Tighten all bolts in correct order in two or three steps. Refer to "ASSEMBLY ".

   Fig 1: Identifying Main Bearing

   Courtesy of NISSAN MOTOR CO., U.S.A.
3. Measure inner diameter "A" of each main bearing.
   Fig 2: Measuring Inner Diameter Of Each Main Bearing

   Courtesy of NISSAN MOTOR CO., U.S.A.
4. Measure outer diameter "Dm" of each main journal in crankshaft.
   Fig 3: Measuring Outer Diameter Of Each Main Journal In Crankshaft

   Courtesy of NISSAN MOTOR CO., U.S.A.
5. Calculate main bearing clearance.
   1. Main bearing clearance = A - Dm 
      1. Standard : 0.018 - 0.042 mm (0.0007 - 0.0017 in) 
      2. Limit : 0.1 mm (0.004 in) 
   • If it exceeds the limit, replace bearing.
   • If clearance cannot be adjusted within standard of any bearing, grind crankshaft journal and use undersized bearing.

   When grinding crank pin and crank journal:

   • Grind until clearance is within specified standard bearing clearance.
   • Fillets should be finished as shown in the figure. R: 2.3 - 2.5 mm (0.091 - 0.098 in)
   Fig 4: Main Journal And Pin Journal Fillets
   Courtesy of NISSAN MOTOR CO., U.S.A.

   Refer to "BEARING CLEARANCE " for standard bearing clearance and available spare parts.

6. If the crankshaft is replaced, select thickness of main bearings as follows:
   1. Grade number of each cylinder block main journal is punched on the respective cylinder block. These numbers are punched in either Arabic or Roman numerals.
   2. Grade number of each crankshaft main journal is punched on the respective crankshaft. These numbers are punched in either Arabic or Roman numerals.
      Fig 5: Identifying Grade Number Of Each Cylinder Block Main Journal

      Courtesy of NISSAN MOTOR CO., U.S.A.
      Fig 6: Identifying Crankshaft Journal Grade Number

      Courtesy of NISSAN MOTOR CO., U.S.A.
   3. Select main bearing with suitable thickness according to the following table.
      Fig 7: Identifying Main Bearing

      Courtesy of NISSAN MOTOR CO., U.S.A.

Fig 8: Crankshaft Main Journal Grade Number And Cylinder Block Main Journal Grade Number Chart

Courtesy of NISSAN MOTOR CO., U.S.A.

Main bearing grade color: 

For example:

Cylinder block main journal grade number: 1

Crankshaft main journal grade number: 2

Main bearing grade number = 1 + 2 = 3 (Yellow)