G3406 Engine Caterpillar

Valve Lash Check

Measure the valve lash between the rocker arm and the valve bridge. Perform checks and adjustments with the engine stopped. The valves must be fully closed. To determine whether the valves are fully closed, refer to Testing And Adjusting, "Finding the Top Center Position for the No. 1 Piston" and Testing And Adjusting, "Crankshaft Position for Valve Lash Setting".

An adjustment is NOT NECESSARY if the valve lash is within the tolerance that is listed in Table 1.

If the measurement is not within tolerance, adjust the valve bridge and then adjust the valve lash.

Valve Bridge Adjustment

When the head is disassembled, mark the valve bridges for the respective cylinders. Adjustment of the bridge will be necessary after grinding of the valves or other reconditioning of the cylinder head.

The valve bridge must be adjusted before the valve lash is adjusted. The valve bridge can be adjusted without removal of the rocker arms and shafts.

Use the following procedure to adjust the valve bridges:

1. Remove the valve cover.

2. Ensure that the No. 1 piston is at the top center (TC) position. Refer to Testing And Adjusting, "Finding the Top Center Position for the No. 1 Piston".

3. Work on the appropriate cylinders that are listed in Testing and Adjusting, "Crankshaft Positions for Valve Lash Setting".
   Show/hide table

   Illustration 1	g00769483
   (1) Locknut (2) Adjustment screw (3) Valve bridge (4) Rocker arm (5) Bridge dowel

   Note: If the cylinder head is disassembled, keep the valve bridges with the respective valves. Check that bridge dowels (5) are installed to the correct height. Lubricate the bridge dowel, the bore for the bridge dowel, and the top contact surface of the valve bridge. Install the valve bridge on the dowel.

4. Loosen locknut (1) and adjusting screw (2).

5. Press straight down on rocker arm (4) at the contact point for valve bridge (3). Turn adjusting screw (2) clockwise until the screw just contacts the valve stem.

6. Tighten adjusting screw (2) for an additional 25 ± 5 degrees in order to straighten the valve bridge onto the dowel.

   This also compensates for slack in the threads of the adjustment screw.

7. Hold adjusting screw (2) in position and tighten locknut (1) to 47 ± 9 N·m (35 ± 7 lb ft).

8. Ensure that the valve lash is correct. Refer to "Valve Lash Check".

9. Install the valve cover.

Valve Lash Adjustment

The valve bridge must be adjusted before the valve lash is adjusted.

1. Ensure that the No. 1 piston is at the top center (TC) position. Refer to Testing And Adjusting, "Finding the Top Center Position for the No. 1 Piston".

2. Work on the appropriate cylinders that are listed in Testing and Adjusting, "Crankshaft Positions for Valve Lash Setting".
   Show/hide table

   Illustration 2	g00769478
   (1) Locknut (2) Adjustment screw (3) Rocker arm (4) Wear seat

3. Loosen locknut (1) and adjusting screw (2).

4. Insert the appropriate feeler gauge between rocker arm (3) and wear seat (4). Refer to Table 2.
   Show/hide table

   Table 2

   Valve Lash Setting
   Inlet	0.38 ± 0.10 mm (0.015 ± 0.004 inch)
   Exhaust	1.02 ± 0.10 mm (0.040 ± 0.004 inch)

5. Hold adjusting screw (2) in place and tighten locknut (1) to a torque of 30 ± 4 N·m (22 ± 3 lb ft).

6. Verify that the setting is correct.

7. Remove the timing bolt from the flywheel housing. Rotate the crankshaft for 360 degrees. Install the timing bolt in the flywheel housing.

8. With the No. 1 piston in the top center of the opposite stroke, perform Steps 1 through 7 for the remaining cylinders.

9. Remove the timing bolt from the flywheel housing.