Piston To Cylinder Bore Clearance

Inner Diameter of Cylinder Bore

• Using a bore gauge, measure cylinder bore for wear, out-of-round and taper at 6 different points on each cylinder. (X and Y directions at A, B and C). The Y axis is in the longitudinal direction of the engine.
  NOTE: When determining cylinder bore grade, measure cylinder bore at B position. Refer to "STANDARD AND LIMIT ".
• If the measured value rebore exceeds the limit, or if there are scratches and/or seizure on the cylinder inner wall, hone the inner wall.
  Fig 1: Measuring Cylinder Bore For Wear, Out-Of-Round And Taper At Six Different Points

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

Outer Diameter of Piston

• Measure piston skirt diameter using a micrometer. Refer to "STANDARD AND LIMIT ".
  Fig 2: Measuring Piston Skirt Diameter Using Micrometer

  Courtesy of NISSAN MOTOR CO., U.S.A.
• Measure point (distance from the top): 42 mm (1.65 in)

Piston to Cylinder Bore Clearance

• Calculate by outer diameter of piston skirt and inner diameter of cylinder (direction X, position B). (Clearance) = (Inner diameter of cylinder) - (Outer diameter of piston skirt).

  Standard : 0.010 - 0.030 mm (0.0004 - 0.0012 in) 

  Limit : 0.08 mm (0.0031 in) 

• If it exceeds the limit, replace piston/piston pin assembly.

Reboring Cylinder Bore

1. Cylinder bore size is determined by adding piston-to-bore clearance to piston diameter "A".

   Rebored size calculation: D = A + B - C 

   D: Bored diameter 

   A: Piston diameter as measured 

   B: Piston-to-bore clearance (standard value) 

   C: Honing allowance 0.02 mm (0.0008 in) 

2. Install main bearing caps, and tighten to the specified torque. Otherwise, cylinder bores may be distorted in final assembly.
3. Cut cylinder bores.
   • When any cylinder needs boring, all other cylinders must also be bored. 
   • Do not cut too much out of cylinder bore at a time. 
4. Hone cylinders to obtain specified piston-to-bore clearance.
5. Measure finished cylinder bore for out-of-round and taper.
   • Measurement should be done after cylinder bore cools down.