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SERIES 638 CAMSHAFT

The camshaft drive gear, located at the front of the engine, behind the front cover, is driven by the crankshaft through a series of gears. See Figure 28401 . The crankshaft drive gear, mounted on the crankshaft, meshes with both the oil pump and vacuum pump. The vacuum pump drive gear, meshes with the camshaft drive gear which in turn drives the injection pump. ‪

1.Injection Pump Drive Gear ‪

4.Crankshaft Drive Gear ‪

2.Camshaft Drive Gear ‪

5.Vacuum Pump Drive Gear ‪

3.Oil Pump Drive Gear ‪

Engine Gear Train

Repair or Replacement of Camshaft

To determine if repair or replacement of the camshaft is necessary, perform the following procedure. See Figure 28402 . ‪

Flowchart for Repair or Replacement of Camshaft

Removal of Camshaft

Remove the camshaft as follows: ‪

  1. Remove the front cover. Refer to section .
  2. Remove the cylinder head(s). Refer to section .
  3. Remove the hydraulic lifters. Refer to section .
  4. Rotate engine to align camshaft thrust plate retaining bolts with access holes through camshaft gear. See Figure 28400 .

    1.Allen Head Bolt ‪

    2.Camshaft Drive Gear ‪

    Thrust Plate Retaining Screws Location

  5. Remove the two Allen head bolts and lockwashers securing the camshaft to the block thrust plate. See Figure 28403 .

    1.Allen Head Bolt ‪

    4.Camshaft ‪

    2.Lockwasher ‪

    5.Camshaft Key ‪

    3.Thrust Plate ‪

    6.Camshaft Drive Gear ‪

    Camshaft Thrust Plate Location

  6. Remove camshaft assembly from the cylinder block by sliding forward.
  7. Remove the camshaft drive gear and camshaft key.
  8. Remove the thrust plate.
Cleaning of Camshaft

Clean the camshaft assembly as follows: ‪

  1. Remove any dirt or debris from the camshaft assembly using clean fuel oil.

    To avoid personal injury when blow drying, wear adequate eye protection (safety glasses or face plate) and do not exceed 276 kPa (40 lb/in. 2 ) air pressure. ‪

  2. Dry the camshaft assembly with compressed air.
Inspection of Camshaft

Inspect the camshaft as follows: ‪

  1. Visually check the camshaft journals for wear or scuffing.
    1. If the camshaft journals are worn or scuffed, replace the component. Refer to section .
    2. If the camshaft journals are not worn or scuffed, proceed with step of inspection.
  2. Measure the camshaft lobes. See Figure 28405 and compare the measured intake results with the specification values listed in Table and the measured exhaust results with the specification values listed in Table .

    Measuring Camshaft Lobes

    Measurement A"

    Measurement B"

    Lobe Height

    38.50 mm (1.515 in.) ‪

    45.70 mm (1.799 in.) ‪

    7.20 mm (0.283 in.) ‪

    Specification Values for Intake Lobes

    Measurement A"

    Measurement B"

    Lobe Height

    37.50 mm (1.476 in.) ‪

    45.14 mm (1.777 in.) ‪

    7.64 mm (0.301 in) ‪

    Specification Values for Exhaust Lobes
    1. If the camshaft lobes measure less than.05 mm (0.002 in.) of specification, replace the component. Refer to section .
    2. If the camshaft lobes measure within .05 mm (0.002 in.) of specification, proceed with step of inspection.
  3. Measure the camshaft journals and bearings. See Figure 28404 and compare the measured journal and bearing results with the specification values listed in Table .

    Measuring Camshaft Journals and Bearings

    Camshaft Journal

    Bushing Diameter

    Exterior Diameter

    Seat Diameter

    A"53.495-53.510 mm(2.1060-2.1066 in.) ‪

    B"53.545-53.500(2.1080-2.1062 in.) ‪

    C"57.130-57.161 mm(2.2492-2.2504 in.) ‪

    D"57.005 mm(2.2442 in.) ‪

    A1"53.450-53.470 mm(2.1043-2.1051 in.) ‪

    B1"53.410-53.460 mm(2.1027-2.1047 in.) ‪

    - ‪

    - ‪

    A2"53.480-53.500 mm(2.1055-2.1062 in.) ‪

    - ‪

    - ‪

    - ‪

    Specification Values for Journals and Bearings
    1. If the camshaft journal and bearing values are not to specification, replace the component. Refer to section .
    2. If the camshaft journal and bearing values are to specification, proceed with step of inspection.
  4. Measure the camshaft thrust plate thickness. See Figure 28406 . Compare measured results with the values listed in Table .

    Thrust Plate Thickness Measurement

    Thrust Plate Thickness A"

    Thrust Plate Thickness B"

    Thrust Plate Thickness C"

    Thrust Plate Thickness D"

    3.950-4.050 mm (0.1555-0.1594 in.) ‪

    3.950-4.050 mm (0.1555-0.1594 in.) ‪

    3.950-4.050 mm (0.1555-0.1594 in.) ‪

    3.950-4.050 mm (0.1555-0.1594 in.) ‪

    Specification Values for Camshaft Thrust Plate
    1. If thrust plate thickness is not to specification, replace component. Refer to section .
    2. If thrust plate thickness is to specification, reuse component. Refer to section .

Installation of Camshaft

Install the camshaft as follows: ‪

  1. Install the thrust plate onto the camshaft. See Figure 28403 .

    1.Allen Head Bolt ‪

    4.Camshaft ‪

    2.Lockwasher ‪

    5.Camshaft Key ‪

    3.Thrust Plate ‪

    6.Camshaft Drive Gear ‪

    Camshaft Thrust Plate Location

  2. Secure camshaft into a suitable holding device for assembly.

    NOTICE:

    To avoid camshaft end damage, ensure that the camshaft key is positioned correctly before pressing the camshaft drive gear onto the camshaft. ‪

  3. Position the camshaft key onto the camshaft and place the camshaft drive gear to the end of the camshaft. Using a suitable press, press the camshaft gear onto the camshaft.
  4. Install the camshaft into the cylinder block.
  5. Align the thrust plate holes with the camshaft access holes. See Figure 28400 .

    1.Allen Head Bolt ‪

    2.Camshaft Drive Gear ‪

    Thrust Plate Retaining Screws Location

  6. Install and tighten the two Allen head bolts to the camshaft drive gear. Torque to 27-28 Nm (20-21 ftlb).
  7. Install the hydraulic lifters. Refer to section .
  8. Install the cylinder heads. Refer to section .
  9. Install the front cover. Refer to section .
  10. Run the engine to verify repairs.