Case 1150B with Cummins 451 Diesel Engine Performance and Integration

[MikePhua]

The Case 1150B Dozer and Its Industrial Legacy
The Case 1150B crawler dozer was introduced in the late 1970s as part of Case’s push into mid-sized earthmoving equipment. Built by J.I. Case Company, a Wisconsin-based manufacturer with roots dating back to 1842, the 1150B was designed for grading, land clearing, and site preparation. With an operating weight of approximately 28,000 lbs and a blade capacity of 3.5 cubic yards, it became a staple in construction fleets and municipal yards across North America.
The 1150B originally came equipped with a Case-built diesel engine, but many units have since been retrofitted with alternative powerplants, including the Cummins 451—a robust inline-six diesel known for its torque and reliability.
The Cummins 451 Diesel Engine Overview
The Cummins 451, also referred to as the NH series in some configurations, is a naturally aspirated or turbocharged inline-six diesel engine with a displacement of 743 cubic inches (12.2 liters). It was widely used in trucks, industrial equipment, and stationary power units throughout the 1960s and 1970s.
Key specifications:

• Configuration: Inline 6-cylinder
  
• Displacement: 743 cu in (12.2 L)
  
• Bore x Stroke: 5.125 in × 5.00 in
  
• Compression ratio: 17.0:1
  
• Power output: 190–240 HP depending on configuration
  
• Torque: Up to 650 lb-ft at 1,500 RPM
  
• Fuel system: Direct injection with PT pump
  
• Cooling: Liquid-cooled with belt-driven water pump
  

The engine’s reputation for longevity and low-end torque made it a popular choice for retrofits in older dozers, especially when original engines became obsolete or parts became scarce.
Engine Swap Considerations and Mounting Challenges
Installing a Cummins 451 into a Case 1150B requires careful planning. The engine block is significantly larger than the original Case diesel, and mounting points, bellhousing alignment, and cooling system integration must be addressed.
Common retrofit steps:

• Fabricate custom engine mounts using ½-inch steel plate
  
• Adapt bellhousing to match transmission input shaft
  
• Modify exhaust routing to clear frame and blade lift cylinders
  
• Upgrade radiator and fan shroud to handle increased heat load
  
• Rewire starter and alternator circuits to match 12V system
  
• Install new throttle linkage and governor control
  

In one retrofit project in Montana, a contractor used a donor engine from a retired Kenworth truck and fabricated a custom bellhousing adapter using a CNC-machined aluminum plate. The result was a seamless integration with the Case transmission and improved fuel economy under load.
Performance Gains and Operational Impact
The Cummins 451 offers significantly more torque than the original Case engine, especially at low RPM. This translates into better pushing power, smoother grading, and improved performance in clay and rocky soils.
Observed benefits:

• Faster blade response under load
  
• Reduced stalling during uphill grading
  
• Improved fuel efficiency at partial throttle
  
• Lower engine temperatures due to larger cooling capacity
  
• Easier cold starts with upgraded glow plug system
  

Operators report that the engine’s torque curve allows them to work at lower RPMs without sacrificing productivity, reducing wear on drivetrain components and extending service intervals.
Fuel System and Maintenance Considerations
The Cummins PT (pressure-time) fuel system is unique and requires specific maintenance protocols. Unlike conventional injection pumps, the PT system uses a gear-driven pump and timed injectors to deliver fuel based on pressure and engine speed.
Maintenance tips:

• Replace fuel filters every 250 hours
  
• Inspect injector lines for leaks or abrasion
  
• Test fuel pressure at idle and full throttle (typically 250–300 psi)
  
• Use high-quality diesel with lubricity additives
  
• Drain water separator weekly in humid climates
  

A fleet manager in Ontario noted that switching to synthetic oil and upgrading the fuel filtration system reduced injector wear and improved throttle response in cold weather.
Cooling System and Thermal Management
The larger displacement of the Cummins 451 generates more heat, especially during heavy grading or summer operations. Cooling upgrades are essential to prevent overheating and maintain engine longevity.
Recommended cooling enhancements:

• Install high-capacity radiator with 4-row core
  
• Use silicone hoses and stainless clamps for durability
  
• Add coolant filter to remove scale and debris
  
• Monitor coolant temperature with digital gauge
  
• Flush system annually and use extended-life coolant
  

In one case, a forestry crew in Oregon added a hydraulic-driven fan with variable speed control, allowing the engine to maintain optimal temperature even during prolonged mulching operations.
Operator Stories and Field Performance
In 2019, a land clearing company in Georgia retrofitted three Case 1150Bs with Cummins 451 engines sourced from retired fire trucks. After adapting the mounts and cooling systems, the machines were deployed in clay-heavy terrain. Operators reported a 20% increase in productivity and fewer breakdowns compared to the original engines.
Another story comes from a restoration shop in Alberta, where a 1150B was rebuilt for resale. The Cummins engine was paired with a rebuilt transmission and upgraded hydraulics. The machine sold within two weeks to a contractor specializing in slope stabilization.
Conclusion and Recommendations
Retrofitting a Case 1150B with a Cummins 451 diesel engine offers substantial performance gains, improved reliability, and extended service life. While the swap requires fabrication and careful integration, the result is a dozer capable of handling modern workloads with vintage toughness.
Recommendations include:

• Source engines with known service history and compression test results
  
• Upgrade cooling and fuel systems to match engine demands
  
• Use OEM-quality mounts and adapters for vibration control
  
• Monitor fuel pressure and injector performance regularly
  
• Document all modifications for future service and resale
  

With the right setup, the Case 1150B becomes more than a legacy machine—it becomes a modernized workhorse ready to tackle the toughest terrain with confidence.