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Cummins 4BT Engine Jeep Swaps

Cummins 4BT Engine History

Cummins 4BT Jeep SwapThe Cummins 4BT Engine (3.9 L) originally was created for industrial applications. This small diesel made its debut in 1983 as a part of the popular B Series of Cummins Engines. The 4BT was installed primarily in Bread Trucks and Step Vans to haul freight around cities. This is engine should be name Old Reliable because it will run forever. The B50 Life Expectancy before overhaul is roughly 400,000 miles. This engine is known for is reliability as there is no electronic parts on the engine minus the starter and fuel-shut off solenoid. There is no reason this engine won’t run for 1,000,000+ miles. The standard 4BT was produced from 1983-1998. The post 1998 models, known as the 4BTA, are a 16 valve 170 hp 420 lb-ft of torque.

The Off-Roading Community began installing Cummins 4BT Engines into Jeeps starting back in the 1980s for four reasons:

  • Significant Torque Ratio Upgrade Over Gas Engines
  • Biggest Diesel Engine That Will Fit Automotive Applications
  • Greater Fuel Economy
  • Long Life Expectancy and Room For Performance Upgrades

Engine Specs and Fuel Economy

Off-Roading AdventuresThe Cummins 4BT engine is not known for his raw power only pulling 105 horsepower @ 2,300 rpm however the torque ratio is 265 lb-ft of torque @ 1,600 rpm. With some common performance upgrades this engine will pull 750 lb-ft of torque. Torque is the amount of force all 4 four wheels will produce at the point of contact on the ground. This is important for off-roading as a matter of a few inches is the difference between getting over that incline or ending up in the mud. The standard 4BT will 18-20 mpg in the city and 22-25 mpg on the highway. A normal upgraded engine will yield 28 – 30 mpg with some high level performance mods to the aftercooler, turbo and variable timing of the camshaft being able to get 35 - 40 mpg. Note that up performance mods like that are quite expensive. Be prepared to pay a great deal of money for something like that.

Injection Pump Options

P7100 Cummins Diesel PumpThe standard 4BT uses a P7100 Mechanical Fuel Injection Pump while the later models switched to an electronic VP or VE Pumps. The older mechanical pumps are easier to modify and upgrade however you won't get as good of fuel millage out of them. If you are looking for power definitely go with the P7100 as the it pushes more fuel. The downside to P7100 pumps other than fuel economy is that if for any reason the unit breaks a lift pump or has a leak in the fuel line there is no automatic shutoff. Lack of fuel will destroy the pump. With a VE or VP Pump the unit will shut the engine off to save the pump.

Common 4BT Swap Vehicles

The Cummins 4BT Engine can be swapped into almost any 4 x 4 vehicle. Common automotive models include Jeep Wranglers, Jeep Grand Cherokees, Land Rovers, Toyota FJ Cruisers, Toyota 4Runners, Nissan Xterras, Mercedes-Benz G500s, Ford 150s, Ford Raptors, Ford Broncos or Chevy Colorado. The engine is roughly 1/3 of the weight of a Jeep Wrangler so suspension is must when installing this engine. The axles must also be retrofitted. For bigger trucks or SUVs the added weight shouldn't be a huge issue however it is always a smart idea to DIESEL ENGINE OFF-ROADING APPLICATIONSmake sure the chassis is balanced and properly holding the addition weight. The most common is a 4BT Jeep Swap. Check out some of the most popular OHV Trails in Colorado once you get 4BT Swap up and running!

Common Jeep Wrangler 4BT Swap Models Include:

  • CJ 1976 – 1986
  • YJ 1987 – 1995
  • TJ 1997 – 2006
  • XJ/MJ 1984 – 2001
  • KJ/KK 2002 – 2013
  • WJ/WK/WK2/ZJ 1993 – 2015
  • JK 2007 – Present

Cummins 4BT Engines For Sale

4BT DozerWe offer both new surplus longblocks and complete engines also known as (extended longblocks) for sale. In addition to new engines we also sell used and remanufactured options.

  • 4B Longblocks
  • 4B 105 HP (Extended Longblocks)
  • 4B 130 HP (Extended Longblocks)
  • 4B 140 HP (Extended Longblocks)

Click Here to learn more about what our longblock and extended longblocks come with.

Please note that we do not do specialize in 4BT Swaps; we are diesel engine manufacturers and machinists not performance mechanics. If you are a shop specializing in 4BT Swaps let us know and we can ship one of our new, used or remanufactured 4BT engines to your facility. Check out some of our installation partners for info on mods and engine installs.

Cummins 4BT Spec

Engine Data

Configuration Inline 4 Cylinder
Displacement 3.9 L, 239 cubic inches
Bore x Stroke 4.02" x 4.72"
Cylinder Head Cast Iron
Engine Block Cast Iron
Firing Order 1-3-4-2
Compression Ratio 17.5 : 1
Injection Direct Injection, Mechanical Injection Pump
Aspiration Turbocharged, non-intercooled
Valve Train OHV, 2 valves per cylinder
Weight 745-782 lbs with oil
Oil Capacity 10 quarts
Governor Speed Varies with application
Horsepower 105 hp @ 2300 rpm
Torque 265 lb-ft @ 1600 rpm


Give us a call today at 844-340-4114 for immediate sales and support for the Cummins 4BT, Cummins 6BT or CAT 3306. If you have any questions check out our FAQ Page. We are always ready to help or just listen to your crazy off-roading adventures!

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Cummins 4BT Engines
4BT Extended Longblock (Bosch Injectors)
4BTAA Extended Long Block (Rotary)
Cummins 6BT Extended Longblock
Caterpillar 3306 Complete Engine
Cummins 4BT Dozer Application
Cummins 4BT Jeep Swap Engine
Cummins 4BT Skid Steer Engine

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