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Cylinder Block And Piston

  1. Visually inspect to make sure that there are no cracks, scratches or other damage.
  2. Use liquid penetrant tester on the important sections to check for fissures.
  3. Check that there are no traces of gas leaking or water leaking on the gasket attachment surface.
  4. Check the oil passages for clogging.
  5. Check for warpage of mating surfaces of the cylinder block that contacts cylinder head using a straight edge and thickness gauge. If it exceeds the limit, correct the surface by grinding it with a surface grinder or replace the cylinder block.
    NOTE: Measurement should be performed at a temperature of 20°C (68°F).

    Cylinder block warpage: 

    Limit 

    0.025 mm (0.0010 in)

    Grinding limit of cylinder block: 

    204.95 mm (8.0689 in) or less

    Height of cylinder block: 

    Standard 

    205.0 mm (8.0709 in)

  6. Using a cylinder bore gauge, check the cylindricality and out-of-roundness of cylinder liner. If they are not within the standard, perform reboring (including honing), or replace the cylinder block and piston as a set. For reboring and honing procedure, refer to step 8.
    NOTE:
    • Measure the cylinder liner with cylinder blocks separated (into cylinder block RH and cylinder block LH).
    • Measurement should be performed at a temperature of 20°C (68°F).
    • Write down all measurement values as the values are used in the next procedure.
    • Measure the inner diameter of each cylinder liner in both the thrust and piston pin directions at the heights as shown in the figure.
    • Calculate the cylindricality of cylinder liner by using the following formula.
      G13868164Courtesy of SUBARU OF AMERICA, INC.
      Calculation formula
      C = The larger value between the calculation values C' and C"
      C' = (D (a) - D (b))/2
      C' = (D (c) - D (d))/2
      C: Cylindricality of cylinder liner
      D (a): The largest value of all the values obtained by measuring the cylinder liner inner diameter in the direction of the piston pin
      D (b): The smallest value of all the values obtained by measuring the cylinder liner inner diameter in the direction of the piston pin
      D (c): The largest value of all the values obtained by measuring the cylinder liner inner diameter in the thrust direction
      D (d): The smallest value of all the values obtained by measuring the cylinder liner inner diameter in the thrust direction
    • Calculate the out-of-roundness of cylinder liner at each measurement height by using the following formula.
      Calculation formula
      R = (D (e) - D (f))/2
      R: Out-of-roundness of cylinder liner
      D (e): The larger value between the measurement values in the piston pin direction and in the thrust direction of cylinder liner inner diameter
      D (f): The smaller value between the measurement values in the piston pin direction and in the thrust direction of cylinder liner inner diameter

    Cylindricality of cylinder liner: 

    Limit 

    0.030 mm (0.0012 in)

    Out-of-roundness of cylinder liner: 

    Limit 

    0.030 mm (0.0012 in)

  7. Check the clearance between cylinder liner and piston. Check the clearance between cylinder liner and piston by measuring the inner diameter of cylinder liner and the outer diameter of piston respectively.
    1. Measure the inner diameter of cylinder liner. If they are not within the standard, perform reboring (including honing), or replace the cylinder block and piston as a set. For reboring and honing procedure, refer to step 8.
      NOTE:
      • Measure the cylinder liner with cylinder blocks separated (into cylinder block RH and cylinder block LH).
      • Measurement should be performed at a temperature of 20°C (68°F).
      • The cylinder bore size mark is stamped on the upper face of the cylinder block.
        G13868165Courtesy of SUBARU OF AMERICA, INC.
      • Measure the inner diameter of each cylinder liner in both the thrust and piston pin directions at the heights as shown in the figure and read the value of the most worn location.
        G13868166Courtesy of SUBARU OF AMERICA, INC.

      Inner diameter of cylinder liner: 

      Cylinder bore size mark A 

      Standard 

      94.005 - 94.015 mm (3.7010 - 3.7014 in)

      Cylinder bore size mark B 

      Standard 

      93.995 - 94.005 mm (3.7006 - 3.7010 in)

    2. Check the outer diameter of piston with a micrometer. If it is not within the standard, replace the piston.
      NOTE:
      • Measurement should be performed at a temperature of 20°C (68°F).
      • Measure the outer diameter of each piston in thrust direction at the height as shown in the figure.
      • Standard sized pistons are classified into two grades, "A" and "B". These grades should be used as guide lines in selecting a standard piston.
      • The grade can be judged by the stamp of cylinder bore size mark on the upper face of the cylinder block.
        G13868167Courtesy of SUBARU OF AMERICA, INC.
      • If the piston is replaced, check the clearance between cylinder liner and piston in the step (3), and select a suitable sized piston.

      Piston grade point H: 

      13.3 mm (0.5236 in)

      Piston outer diameter: 

      Standard size (grade A = cylinder bore size mark A) 

      Standard 

      93.980 - 93.990 mm (3.7000 - 3.7004 in)

      Standard size (grade B = cylinder bore size mark B) 

      Standard 

      93.970 - 93.980 mm (3.6996 - 3.7000 in)

      G13224608Courtesy of SUBARU OF AMERICA, INC.
    3. Calculate the clearance between cylinder liner and piston. If they are not within the standard, perform reboring (including honing), or replace the cylinder block and piston as a set. For reboring and honing procedure, refer to step 8.
      NOTE: The clearance between cylinder liner and piston is decided by matching the cylinder block bore size mark and the grade of piston outer diameter (grade A or B).

      Clearance between cylinder liner and piston: 

      Standard 

      0.015 - 0.035 mm (0.0006 - 0.0014 in)

  8. Reboring and honing
    1. If any of the cylindricality, out-of-roundness, inner diameter or clearance between cylinder liner and piston is out of standard or if there is any damage on the cylinder liner, perform reboring (including honing).
      CAUTION: When any of the cylinder liner needs reboring, all other cylinder liners must be rebored at the same time, and replaced with proper size pistons.

      Oversize piston outer diameter: 

      0.25 mm (0.0098 in) oversize 

      Standard 

      94.220 - 94.240 mm (3.7094 - 3.7102 in)

      0.50 mm (0.0197 in) oversize 

      Standard 

      94.470 - 94.490 mm (3.7193 - 3.7201 in)

    2. If the inner diameter of cylinder liner exceeds the limit after reboring (including honing), replace the cylinder block and piston as a set.
      NOTE:
      • Immediately after reboring (including honing), the inner diameter of cylinder liner may differ from its real diameter due to temperature rise. Thus, when measuring the inner diameter of cylinder liner, wait until the temperature has cooled to 20°C (68°F).
      • For the measurement of the inner diameter of cylinder liner, refer to step 7.

      Inner diameter of cylinder liner boring limit (diameter): 

      94.505 mm (3.7207 in) or less

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