3408 & 3408B DIESEL TRUCK ENGINE Caterpillar


Camshaft

Usage:

(1) Maximum permissible temperature of the gear for installation on the camshaft (do not use a torch) ... 316° C (600° F).

(2) Interference fit between the gear and camshaft ... 0.062 to 0.138 mm (.0024 to .0054 in.)

(3) Diameter of the surfaces (journals) for the camshaft bearings (new) ... 69.850 ± 0.013 mm (2.7500 ± .0005 in.)

Bore in front and rear bearings for the camshaft (new) ... 69.969 ± 0.048 mm (2.7547 ± .0019 in.)

Bore in inner bearings for the camshaft (new) ... 69.982 ± 0.061 mm (2.7552 ± .0024 in.)

(4) Thickness of thrust plate (new) ... 4.65 ± 0.03 mm (.183 ± .001 in.)

End play of the camshaft ... 0.10 to 0.25 mm (.004 to .010 in.)

(5) Height of camshaft lobes.

To find lobe height, use the following procedure:

A. Measure camshaft lobe height (5).

B. Measure base circle (7).

C. Subtract base circle (Step B) from lobe height (Step A). The difference is actual lobe lift.

D. Specified camshaft lobe lift (6) is:

a. Exhaust lobe ... 8.783 mm (.3458 in.)
b. Intake lobe ... 8.100 mm (.3189 in.)

Maximum permissible difference between actual lobe lift (Step C) and specified lobe lift (Step D) is 0.13 mm (.005 in.)

Intake Valve Timing

1. Check the No. 1 intake valve clearance with the engine stopped. The valve clearance must be .030 to 0.46 mm (.012 to .018 in.). If the valve clearance is not in this range, adjust the clearance to 0.38 mm (.015 in.).

2. Mark Top Center Position of the crankshaft on the vibration damper or pulley.

3. Use a dial indicator to measure the intake valve movement.

4. Rotate the crankshaft in the direction of normal engine rotation. Stop when the intake valve is 1.91 mm (.075 in.) off its seat in the opening sequence.

At this point the crankshaft Top Center Position Mark must be ... 3 ± 2° After Top Center

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