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C3.3B Tier 4 Interim and EU Stage 3A Engines for Caterpillar Built Machines – Valve Mechanism


Illustration 1g03001816

(1) Rocker Arm

(2) Push Rod

(3) Valve Bridge Arm

Table 1
Valve timing     Intake valve     C2.6 Open - 0.21 rad (12°) before T.D.C
C2.6 Closed - 0.77 rad (44°) after B.D.C
C3.3B Open - 0.24 rad (14°) before T.D.C
C3.3B Closed - 0.70 rad (40°) after B.D.C    
Valve timing     Exhaust valve     C2.6 Open - 0.86 rad (49°) before B.D.C
C2.6 Closed - 0.30 rad (17°) after T.D.C
C3.3B Open - 0.87 rad (50°) before B.D.C
C3.3B Closed - 0.24 rad (14°) after T.D.C    

Table 2
Tightening torque     Rocker arm bracket bolt     C2.6 - 24 to 27 N·m (18 to 20 lb ft)
C3.3B - 49 to 55 N·m (37 to 41 lb ft)    

Oil Clearance between Rocker Arm Shaft and Bearing


    Illustration 2g02997863

  1. Measure the rocker arm bearing inside diameter with an inside micrometer.

  1. Measure the rocker arm shaft outside diameter with an outside micrometer, and then calculate the oil clearance.

    Table 3
    Oil clearance of rocker arm shaft and bearing     New     0.016 to 0.045 mm (0.00063 to 0.0017 inch)    
    Allowable limit 0.15 mm (0.0059 inch)    

    Table 4
    Rocker arm shaft outside diameter     New     C2.6 - 13.973 to 13.984 mm (0.55012 to 0.55055 inch)
    C3.3B - 14.973 to 14.984 mm (0.58949 to 0.58992 inch)    

    Table 5
    Rocker arm inside diameter for shaft     New     C2.6 - 14.000 to 14.018 mm (0.55118 to 0.55189 inch)
    C3.3B - 15.000 to 15.018 mm (0.59056 to 0.59125 inch)    

  1. If the clearance exceeds the allowable limit, replace the rocker arm and measure the oil clearance again. If the clearance still exceeds the allowable limit, replace also the rocker arm shaft.

Oil Clearance between Valve Bridge Arm and Valve Bridge Shaft


    Illustration 3g02997869

    (1) Valve Bridge Arm

  1. Measure the valve bridge arm (1) inside diameter with an inside micrometer.

    Illustration 4g02997872

    (2) Valve Bridge Shaft

  1. Measure the valve bridge shaft (2) outside diameter with an outside micrometer, and then calculate the oil clearance.

    Table 6
    Oil clearance between valve bridge arm and valve bridge shaft     New     C2.6 - 0.018 to 0.057 mm (0.00071 to 0.00224 inch)
    C3.3B - 0.018 to 0.042 mm (0.00071 to 0.0016 inch)    
    Allowable limit 0.15 mm (0.0059 inch)    

    Table 7
    Valve bridge shaft outside diameter     New     C2.6 - 8.023 to 8.032 mm (0.31587 to 0.31622 inch)
    C3.3B - 9.023 to 9.032 mm (0.3553 to 0.3555 inch)    

    Table 8
    Valve bridge arm inside diameter     New     C2.6 - 8.050 to 8.080 mm (0.31693 to 0.31811 inch)
    C3.3B - 9.050 to 9.065 mm (0.3563 to 0.3568 inch)    

Push Rod Alignment


    Illustration 5g02997916

    (1) Pushrod

  1. Place the push rod on V blocks.

  1. Measure the push rod alignment.

    Table 9
    Push rod alignment     Allowable limit     0.25 mm (0.0098 inch)    

Oil Clearance between Tappet and Tappet Bore


    Illustration 6g02997956

    (1) Tappet

  1. Measure the tappet outside diameter with an outside micrometer.

    Illustration 7g02997957

    (2) Tappet Bore

  1. Measure the inside diameter of the tappet bore at the most wear part with a small hole gauge.

    Table 10
    Oil clearance between tappet and tappet bore     New     0.020 to 0.050 mm (0.00079 to 0.0019 inch)    
    Allowable limit 0.07 mm (0.003 inch)    

    Table 11
    Tappet outside diameter     New     9.965 to 9.980 mm (0.3924 to 0.3929 inch)    

    Table 12
    Tappet bore inside diameter     New     10.000 to 10.015 mm (0.39370 to 0.39429 inch)    

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