1969 CAT 951B Engine Valve Adjustment Procedure

[MikePhua]

Overview of the CAT 951B Crawler Loader
The Caterpillar 951B is a legendary crawler loader produced by Caterpillar in the late 1960s. Known for its solid performance in tough conditions, the 951B was a popular choice in construction and mining applications. It was powered by a robust 6-cylinder engine and was a part of the Caterpillar’s medium-duty track loader series. The 951B became a staple in the industry due to its versatility, reliability, and relatively compact size compared to larger equipment.
Over the years, the 951B has been used for digging, lifting, and material handling tasks. However, like all machines of its age, regular maintenance, including valve adjustments, is necessary to keep the engine running smoothly and efficiently. This article will delve into the procedure for adjusting the engine valves of a 1969 CAT 951B, highlighting key considerations and providing practical tips.
Why Valve Adjustment is Necessary
The engine valves in any machine, including the CAT 951B, play a crucial role in regulating the intake and exhaust of gases in the engine. Over time, these valves can wear and become misaligned due to the constant pressure and heat in the engine. Misadjusted valves can lead to:

• Poor engine performance: Valves that do not open or close at the correct times can cause a loss of power and efficiency.
  
• Increased fuel consumption: Improper valve clearance can disrupt the combustion process, resulting in incomplete burning of fuel.
  
• Engine damage: Over time, excessive wear on valves can cause them to become damaged, leading to more costly repairs.
  

Proper valve adjustment ensures optimal engine performance, reduces the risk of engine damage, and enhances the machine's longevity.
Tools and Equipment Required for Valve Adjustment
Before beginning the valve adjustment procedure, it’s important to gather all necessary tools. These include:

• Torque wrench
  
• Feeler gauge set
  
• Screwdriver or wrench to remove valve cover
  
• Socket set
  
• Engine manual for specific valve clearance measurements
  

Having the correct tools will ensure that the procedure is carried out correctly and safely.
Step-by-Step Valve Adjustment Procedure
The following is a general guide to adjusting the engine valves on a 1969 CAT 951B:

1. Preparation:
   • Ensure the engine is cool before starting the procedure to avoid burns and ensure accurate measurements. The valve clearance changes when the engine is hot.
     
   • Disconnect the battery to avoid any accidental electrical mishaps while working near the engine.
     
2. Remove Valve Covers:
   • Use a wrench or screwdriver to remove the bolts securing the valve cover. This will expose the valves and rocker arms.
     
3. Position the Engine:
   • Rotate the engine to the top dead center (TDC) on the compression stroke of the cylinder you are working on. TDC is when both the intake and exhaust valves are fully closed. This ensures that the rocker arms are at their highest point and ready for measurement.
     
   • To rotate the engine, you can use a socket wrench on the crankshaft pulley.
     
4. Measure Valve Clearance:
   • Using a feeler gauge, measure the gap between the valve stem and rocker arm. The correct valve clearance is specified in the engine manual. Typically, valve clearance for Caterpillar engines is between 0.010” and 0.020”.
     
   • Insert the feeler gauge into the gap, ensuring that the gauge can slide with slight resistance. If it is too tight or too loose, the valve clearance is incorrect.
     
5. Adjust Valve Clearance:
   • If the clearance is not correct, use a wrench to adjust the rocker arm nut or valve tappet screw. Tighten or loosen the nut until the correct clearance is achieved.
     
   • It is essential to make adjustments to both the intake and exhaust valves on each cylinder. Repeat the measurement for each valve.
     
6. Recheck Clearances:
   • Once all valves are adjusted, recheck the clearances with the feeler gauge to ensure consistency. Double-check the torque on any nuts that were adjusted during the process.
     
7. Reassemble the Engine:
   • After the valve clearances are adjusted and verified, replace the valve cover, ensuring a proper seal to avoid oil leaks.
     
   • Reconnect the battery and check the engine’s operation. Listen for any abnormal sounds, such as ticking or knocking, which could indicate that the valve adjustment was not properly performed.
     
8. Test the Engine:
   • Start the engine and let it run for a few minutes. Listen for smooth operation and check for signs of poor performance, such as rough idling or misfiring. A successful valve adjustment should lead to a quieter and more efficient engine.
     

Maintenance Tips and Troubleshooting

1. Regular Valve Adjustments:
   Regular valve adjustments are part of the routine maintenance of any older machine like the CAT 951B. It’s generally recommended to check the valve clearance every 500 to 1,000 hours of operation, depending on usage and manufacturer guidelines.
   
2. Listen for Abnormal Sounds:
   If the engine begins to make unusual noises after an adjustment, such as ticking or grinding, it may indicate that the valve clearance is too tight or too loose. This can lead to engine damage if not addressed promptly.
   
3. Keep the Engine Clean:
   Keep the engine and valve areas free of debris and dirt to prevent contamination during the adjustment process. Dirt or particles can cause the valves to wear prematurely or disrupt the engine’s performance.
   

Conclusion
Adjusting the valves on the 1969 CAT 951B crawler loader is a straightforward but critical task for maintaining the machine's engine efficiency and performance. By following a step-by-step procedure and using the proper tools, operators can ensure their machine runs smoothly and efficiently for many years. Regular valve adjustments help maintain optimal engine function, reduce unnecessary fuel consumption, and minimize costly repairs down the line.
Understanding the maintenance needs of older machines like the CAT 951B is essential for ensuring they remain reliable workhorses on job sites. With proper care and attention, these classic machines can continue to deliver excellent performance, even decades after their production.