C3.3B Tier 4 Interim and EU Stage 3A Engines for Caterpillar Built Machines – Cylinder Head Valves

Valve Recessing

  1. Clean the cylinder head, the valve face, and seat.

  1. Insert the valve into the valve guide.

    Illustration 1g02997116

    Illustration 2g02997118

    (A) Recessing

    (B) Protrusion

    (1) Cylinder Head Surface

  1. Measure the valve recessing with a depth gauge.

    Table 1
    Valve recessing (Intake and exhaust)     New     (recessing) 0.65 to 0.85 mm (0.026 to 0.033 inch)    
    Allowable limit (recessing) 1.20 mm (0.0472 inch)    

  1. If the measurement still exceeds the allowable limit after replacing the valve, replace the cylinder head.

Valve Lapping

Illustration 3g02997282

    Illustration 4g02997286

    (1) Correct

    (2) Incorrect

    (3) Incorrect

  1. Apply compound evenly to the valve lapping surface.

  1. Insert the valve into the valve guide. Lap the valve onto its seat with a valve flapper or screwdriver.

  1. After lapping the valve, wash the compound away and apply oil, then repeat valve lapping with oil.

  1. Apply blue to the contact surface to check the seated rate. If it is less than 70 percent, repeat valve lapping again.

    Note: When valve lapping is performed, be sure to check the valve recessing and adjust the valve clearance after assembling the valve.

Clearance between Valve Stem and Valve Guide

  1. Remove carbon from the valve guide section.

    Illustration 5g02997340

  1. Measure the valve stem outside diameter with an outside micrometer.

    Illustration 6g02997343

  1. Measure the valve guide inside diameter of the cylinder head at the most wear part as shown in the figure below with a small hole gauge. And calculate the clearance.

    Table 2
    Clearance between valve stem and guide     New     Intake - 0.030 to 0.057 mm (0.00118 to 0.00224 inch)    
    Exhaust - 0.045 to 0.072 mm (0.00177 to 0.00283 inch)
    Valve stem outside diameter     New     Intake - 5.968 to 5.980 mm (0.23496 to 0.23543 inch)    
    Exhaust - 5.953 to 5.965 mm (0.23437 to 0.23484 inch)

    Valve guide inside diameter (Intake and exhaust)     New     6.101 to 6.025 mm (0.24020 to 0.23720 inch)    

    Table 3
    Clearance between valve stem and guide (Intake and exhaust)     New     0.055 to 0.085 mm (0.0022 to 0.0033 inch)    
    Allowable limit 0.10 mm (0.0039 inch)    
    Valve stem outside diameter (Intake and exhaust)     New     6.960 to 6.975 mm (0.2741 to 0.2746 inch)    
    Valve guide inside diameter (Intake and exhaust)     New     7.030 to 7.045 mm (0.2768 to 0.2773 inch)    

Correcting Valve and Valve Seat

Note: Before correcting the valve and seat, check the valve stem and the inside diameter of valve guide section, and repair them if necessary.

Note: After correcting the valve seat, be sure to check the valve recessing.

Correcting Valve

  1. Correct the valve with a valve refacer.

    Table 4
    Valve face angle (Intake and exhaust)     New     0.79 rad 45 degrees    

Correcting Valve Seat

    Illustration 7g02997579

    (a) 0.26 rad (15 degrees)

    (b) 0.79 rad (45 degrees)

    Illustration 8g02997482

    (1) Valve Seat Width

    (2) Identical Dimensions

    (A) Check Contact

    (B) Correct Seat Width

    (C) Check Contact

    (c) 0.52 rad (30 degrees)

  1. Slightly correct the seat surface with a 0.79 rad (45 degrees) valve seat cutter.

  1. Resurface the seat surface with a 0.26 rad (15 degrees) valve seat cutter so that the width is close to specified valve seat width.

    Table 5
    Valve seat width (Intake and exhaust)     New     3.3 to 3.6 mm (0.13 to 0.14 inch)    

  1. After resurfacing the seat, inspect for even valve seating, apply a thin film of compound between the valve face and valve seat, and fit them with valve lapping tool.

  1. Check the valve seating with blue. The valve seating surface should show good contact all the way around.

    Table 6
    Valve seat angle (Intake and exhaust)     New     0.79 rad 45 degrees    

Valve Springs

    Illustration 9g02997638

    (A) Tilt

    (B) Free Length

  1. Measure the free length (B) with vernier calipers. If the measurement is less than the allowable limit, replace the spring.

  1. Put the spring on a surface plate, place a square on the side of the spring, and check to see if the entire side is contact with the square. Rotate the spring and measure the maximum tilt (A). If the measurement exceeds the allowable limit, replace.

    Table 7
    Tilt (A)     Allowable limit     1.0 mm (0.039 inch)    

    Table 8
    Free length (B)     New     C2.6 - 35.4 mm to 35.9 mm (1.39370 to 1.41338 inch)
    C3.3B - 35.1 to 35.6 mm (1.39 to 1.40 inch)    
    Allowable limit 34.6 mm (1.36 inch)    

  1. Check the entire surface of the spring for scratches. Replace the spring, if any.

Valve Spring Setting Load

    Illustration 10g02997741

  1. Place the valve spring on a tester and compress the spring to the same length the spring is compressed in the engine.

  1. Read the compression load on the gauge.

    Table 9
    Setting load / setting length     New     C2.6 - 60.8 N / 29.7 mm (13.7 lbf / 1.17 inch)
    C3.3B - 63.5 N / 31.5 mm (14.3 lbf / 1.24 inch)    
    Allowable limit C2.6 - 45.9 N / 29.7 (10.3lbf / 1.17 inch)
    C3.3B - 45.9 N / 31.5 mm (10.3 lbf / 1.24 inch)


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