International TD-20B Dozer and DT-429 Engine Push Rod Replacement

[MikePhua]

The TD-20B and Its Historical Role in Earthmoving
The International Harvester TD-20B crawler dozer was introduced in the late 1960s as part of IH’s push into mid-to-heavy class earthmoving equipment. With an operating weight of approximately 20 tons and powered by the DT-429 diesel engine, the TD-20B was designed for grading, ripping, and bulk material movement in construction and mining. International Harvester, founded in 1902, had a long legacy in agricultural and industrial machinery, and the TD-20 series became a workhorse in North America and overseas markets.
The DT-429 engine is a turbocharged inline-six diesel known for its torque output and mechanical simplicity. It was used in several IH machines, including dozers, loaders, and agricultural tractors. The engine’s overhead valve design includes individual push rods that actuate the rocker arms, controlling intake and exhaust valve timing.
Push Rod Identification and Replacement Challenges
One common issue with aging DT-429 engines is push rod wear or bending, often caused by valve sticking, improper valve lash adjustment, or foreign object intrusion. When a push rod fails, the engine may misfire, lose compression in one cylinder, or produce abnormal valve train noise.
Operators seeking to replace a push rod must first identify the correct part number. This can be challenging due to:

• Discontinued parts catalogs
  
• Multiple engine variants with different rod lengths
  
• Confusion between DT-429 and DT-466 components
  

To ensure accuracy, technicians should reference the engine serial number, which is typically stamped on the block near the injection pump. With this number, parts suppliers can cross-reference the correct rod length and tip configuration.
Disassembly and Inspection Procedure
Replacing a push rod involves:

• Removing the valve cover
  
• Rotating the engine to TDC for the affected cylinder
  
• Loosening the rocker arm assembly
  
• Extracting the damaged push rod
  
• Inspecting the tappet and rocker arm for wear
  
• Installing a new rod and adjusting valve lash
  

Valve lash should be set cold to factory specifications—typically around 0.014" for intake and 0.018" for exhaust. Always rotate the engine manually to confirm smooth valve operation before restarting.
Preventive Measures and Engine Longevity
To prevent future push rod failures:

• Perform valve lash adjustments every 500 hours
  
• Use high-quality diesel fuel and maintain injector cleanliness
  
• Replace valve springs and retainers during major overhauls
  
• Avoid over-revving the engine under load
  

One operator in Alberta reported that his TD-20B ran over 8,000 hours with only one push rod replacement, attributing longevity to regular valve checks and clean oil.
Parts Sourcing and Aftermarket Support
While IH no longer produces the TD-20B, parts are still available through:

• Aftermarket suppliers specializing in vintage IH equipment
  
• Salvage yards with donor engines
  
• Custom machine shops that fabricate push rods to spec
  

When ordering, specify:

• Engine model (DT-429)
  
• Rod length and diameter
  
• Tip style (ball or cup)
  
• Application (dozer, loader, tractor)
  

Some suppliers offer hardened push rods for high-load applications, which may improve durability in machines used for ripping or heavy grading.
Conclusion
The TD-20B remains a respected dozer in the legacy of International Harvester, and its DT-429 engine continues to serve in field operations. Replacing a push rod is a straightforward but precision-sensitive task, requiring accurate part identification and careful valve train inspection. With proper maintenance and sourcing strategy, operators can keep these machines running reliably for decades.