Valve Lash Specifications and Adjustment for John Deere 644E Wheel Loader

[MikePhua]

Introduction
The John Deere 644E wheel loader, produced during the late 1980s and early 1990s, is equipped with the 6466T turbocharged six-cylinder engine. Regular maintenance, including valve lash (clearance) adjustments, is crucial to ensure optimal engine performance and longevity.
Valve Lash Specifications
For the 6466T engine, the recommended cold valve lash specifications are:

• Intake Valve Clearance: 0.016–0.020 inches (0.41–0.51 mm)
  
• Exhaust Valve Clearance: 0.026–0.030 inches (0.66–0.76 mm)
  

These measurements are taken between the rocker arm and the valve stem when the engine is cold. Maintaining these clearances ensures proper valve operation, preventing issues like valve burning or poor engine efficiency.
Valve Lash Adjustment Procedure
To adjust the valve lash on the 6466T engine:

1. Preparation: Ensure the engine is cold to prevent inaccurate measurements.
   
2. Positioning the Engine: Rotate the engine to position the No. 1 piston at Top Dead Center (TDC) on its compression stroke.
   
3. Checking Valve Clearance: With the No. 1 piston at TDC, check the clearance on the intake and exhaust valves for cylinders 1, 3, and 5.
   
4. Adjusting Valve Lash:
   • Loosen the lock nut on the rocker arm adjusting screw.
     
   • Turn the adjusting screw until a feeler gauge of the specified thickness slides between the rocker arm and valve stem with slight resistance.
     
   • Hold the adjusting screw in place and tighten the lock nut to the specified torque.
     
5. Rechecking Clearance: After tightening, recheck the valve clearance to ensure it remains within specifications.
   
6. Repeat for Other Cylinders: Rotate the engine 360° to position the No. 6 piston at TDC on its compression stroke. Check and adjust the valve lash for cylinders 2, 4, and 6 using the same procedure.
   

Torque Specifications
When reassembling components, adhere to the following torque specifications:

• Rocker Arm Shaft Clamps: 55 ft-lb
  
• Rocker Arm Cover Bolts: 8–12 ft-lb
  

These torque values ensure secure fastening without damaging components.
Maintenance Tips

• Regular Inspections: Check valve lash at regular intervals as specified in the operator's manual.
  
• Use Proper Tools: Utilize a quality feeler gauge and torque wrench to achieve accurate adjustments.
  
• Document Adjustments: Keep records of valve lash adjustments for future reference and maintenance planning.
  

Conclusion
Adhering to the recommended valve lash specifications and adjustment procedures is vital for maintaining the performance and longevity of the John Deere 644E wheel loader's engine. Regular maintenance, including valve lash adjustments, contributes to efficient engine operation and can prevent costly repairs.