Jeep Wrangler driving off-road with a 4BT Cummins engine
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Cummins 4BT Engines and Long Blocks

Replacement Cummins 4BT Engines For Sale

Nationwide Warranty Coverage Red LogoThe Cummins 4BT is one of the most versatile diesel engines ever produced. Its size, weight, horsepower, torque, and durability make it the perfect choice in countless applications, from gen-sets and forestry equipment to marine vessels and step vans. But whether the 4BT’s industrial work ethic is put to use in an on-road or enthusiast-style off-road application such as a Jeep, you get a fuel-efficient workhorse that will provide gobs of low-rpm torque and hundreds of thousands of miles of trouble-free service. It’s no secret that the 4BT Cummins is our bread and butter here at Big Bear Engine Company, and our long block and extended long block programs are the best in the business. Whether you’re looking for a crate engine, are performing a diesel conversion, or need a fresh engine rebuild, our remanufactured Cummins 4BT (3.9 L) options can get you up and running—and keep you running—for the long-haul.

We offer two types of Cummins 4BT Engines: Long Blocks and Extended Long Block Engines

4BT Long Blocks:

Black Cummins 4BT Engine For Sale on Top of a Wooden Platform

Our long blocks are perfect for someone who already has an older Cummins 4BT and is looking to simply replace the worn hard internal parts of the engine (and then reuse ancillary parts). As a guide, a long block is about 50-percent to 75-percent of a complete engine build. Think of it as the "guts of the engine," but nothing dressing it out. To educate customers—and specifically about long blocks—we have created a 4B long block informational page here. Note, we also offer Cummins 4BT engines for sale, as well as Cummins 4.5 L ISB/QSB long blocks (rear gear train and front gear train). Our traditional long block 4BT Cummins engine includes:

• Engine Block
• Cylinder Head (7mm injector setup)
• Camshaft and Lifters
• Pistons
• Rings
• Oil Pump
• Oil Cooler (later models)
• Crankshaft
• Connecting Rods
• Rocker Assemblies
• Timed Front Gear Group
• Gaskets, Seals, Bearings
• Standard 12 Months Parts Replacement Warranty
• 1 and 2 Year Parts/Labor Extended Warranties also Available
*Note: long blocks may or may not come with a front cover, gear housing, rockers, valve cover or oil pan depending on parts availability

4BT Extended Long Block Engines:

Our component build, extended long block packages come with most everything you need to replace your existing failed engine. These Cummins 4BT Engines are built with brand new ISO 9001 parts (3.9 Cummins) to exact OEM tolerances and have less than a 1-percent parts failure rate. As a guide, a component build is about 90-percent OEM parts and 10-percent aftermarket, when available. These units are perfect for a customer looking to replace an existing 4BT assembly, but who also needs a new turbo or oil pump, etc... As a guide, an extended long block is about 75-percent built out and is best used in conjunction with an existing 4B. Most customers will reuse existing workable parts off of their old engine as needed. We do not sell adapter plates, torque converters, transmissions/PTOs, axles, suspensions, hydroboosts, air cross over tubes, throttle linkages, radiators, differentials or motor mounts with extended long block packages. Additionally, extended long blocks do not come with a starter, alternator, flywheel, or a flywheel housing (SAE#2 or SAE #3), but those items are available for additional, one-off purchase. Most customers reuse those components as they rarely fail. Extended long block builds are run tested prior to shipment. Our extended long block assemblies include:

• Block
• Cylinder Head
• Camshaft and Lifters
• Crankshaft
• Connecting Rods
• Rocker Assemblies
• Gaskets, Rings, Seals, Wrist Pins, Bearings
• Injectors
• Oil Pump and Water PumpAERA Association Member
• Oil Cooler
• Oil Filters
• Oil Pump
• Water Pump
• Intake and Exhaust Manifolds
• Housings (Front and Rear)
• Brackets and Pulleys
• Fuel Pump (Inline or Rotary)
• Fuel Transfer Pump
• Timed Front Gear Group
• Valve Cover
• Turbocharger (HMRO or LMRO Locations)
• Aftercooler (only on some models)
• Air Compressor (only on some models)
• Fan and Fan Shroud (Push or Pull, Some Models Only)
• New Rear Sump Oil Pan and Pickup Tube
• Standard 12 Months Parts Replacement Warranty
• 1 and 2 Year Extended Parts/Labor Warranties also available

What’s New In 4BT Remanufacturing

Something enthusiasts are coming across more and more these days is the fact that their 4BT has already been remanufactured. All engines that’ve been reconditioned by Cummins will have a serial number that begins with a “6” and will look something like this: 60123462. If the original engine has been rebuilt, a remanufacturing tag or plate should be attached, and this is usually placed on the front cover. Additionally, there will be a reconditioned number. This figure often begins with a “DR” designation.

Types Of 4BT’s

Though the industry has settled on referring to all 3.9L Cummins engines as simply the “4BT,” the reality is that that specific acronym only applies to one variation. The best way to understand this is to elaborate on what each acronym associated with the 4BT means. Obviously, the “4” represents the fact that there are four cylinders and the “B” refers to the engine series. However, a 4B designation signifies that the engine is naturally aspirated. Adding the “T” (i.e. 4BT) means the engine utilizes a turbo. From there, the 4BTA enters the picture, and it stands for turbocharged and aftercooled.

4B: naturally aspirated

4BT: turbocharged

4BTA: turbocharged and aftercooled


Common Power Ratings And Fuel Pumps

*4B Power Rating: 76 hp (Inline A-pump)

*4BT Power Rating: 105 hp (Rotary Pump, Inline A-pump)

*4BTA Power Rating: 130 hp (Inline A-pump)

*4BTAA Power Rating: 140 hp (Rotary or Inline P-pump)


What Is A CPL—And Why Is It Important?

Identifying which specific type of Cummins 4BT you have is vital for ordering the correct parts. This is why the acronym “CPL” surfaces so often in Cummins chatter. It stands for control parts list (and is unofficially, yet accurately, often referred to as critical parts list). Because the 4BT was produced in so many different variations (4B, 4BT, 4BTA, high or low-mount turbo, rotary pump or inline pump, different compression ratios, etc.), knowing your engine’s CPL is indispensable. Literally dozens of CPL’s exist for the Cummins 4BT, but one of the more common CPL’s is 767, a standard version of the 4BT which was rotary pumped and produced 105 hp and 265 lb-ft of torque. The CPL tag can typically be found riveted or glued to the front timing cover.


Cummins 4BT Engine Industrial Applications:

Our Cummins 4BT Engines that are for sale are primarily used in industrial applications. The 4BT engine was typically installed in step vans and “bread trucks” for hauling cargo around cities. 4BT Cummins engines are also very common in skid steers, loaders, dozers, forklifts, manlifts, wood chippers, RVs, shuttle vans, pumps, generators, street sweepers and baggage carts. Some Cummins 4BT engines are also in use in small boats and bilge pumps, but most see service in small off-highway equipment.

Cummins 4BT Engine Off-Roading Applications:

Cummins 4BT New Engines The off-roading community has taken quite a liking to the Cummins 4BT engine; known primarily as 4BT Jeep Swaps. The 3.9 Cummins engine won’t win any races as the maximum horsepower is typically only 105 hp at 2,300 rpm, but the engine is extremely popular when it comes to its torque ratio. A standard 4BT will produce 265 lb-ft of torque at 1,600 rpm, but basic upgrades can increase its torque ratio to well over 750 lb-ft. That is a lot of torque at the wheels; and low rpm torque is perfect for traversing steep inclines or hugging the edge of a trail. There is a whole community over at that focuses on all the info you will ever need to swap a 4BT Cummins into an off-road vehicle.

Cummins 4BT engines are also easy to maintain, simplistic in design and can help a vehicle return 30-40 mpg with performance upgrades. The 4BT is the most popular diesel engine swap for off-roading because it is straightforward to upgrade the turbo, camshaft, injectors and fuel pump—and that’s in addition to being the biggest diesel engine packageable in a Jeep or 4Runner. A Cummins 6BT will simply be too large.

Note, long block and extended long block replacement units are sold for use in existing industrial and automotive applications. Intended use of the long block or extended long block package is meant to replace worn or defective existing internal gear train engine components. Bellhousing, fuel systems, solenoids and electrical parts are not included, and are intended for individual one-off parts replacement of existing worn engine components from the customer’s existing engine.

Component Builds do include limited rebuilt and/or remanufactured components when necessary, but frequently they are non-critical wear parts such as aftercoolers, exhaust manifolds, water inlet and outlet connections, gears, gear housings, etc. Each build cycle is different. Component built units are a great alternative to fully remanufactured assemblies where further wear parts are rebuilt to OEM specs. Re-use guidelines govern parts availability and compliance with component built, remanufactured and used assemblies as stated in 40 CFR § 1068.120 "Requirements for Rebuilding Engines".

If extended long block packages are swapped into an off-road utility vehicle or marine application, it is up to the customer to check for local, state and federal regulations in reference to emissions compliance and legal permitting. Big Bear Engine Company is not responsible for any non-intended use of extended long block packages. Each state and even local counties have widely different regulations (classic cars, rat rods, rock crawling vehicles, gross tonnage, number of axles, etc.), so it is always best to do your homework beforehand.

The Legend Behind The 4BT Cummins

Part of the B series line that also featured the popular 6BT (aka 5.9L) Cummins offered in 3/4-ton and 1-ton Dodge Rams, the 4BT Cummins was designed with industrial applications in mind. Even though the 4BT is the little brother of the 6BT, its arrival pre-dates the 6BT, first entering production in July of 1983. For all intents and purposes, the 4BT is 2/3 of a 6BT Cummins engine, which means the same burly, overkill hard parts employed in the 5.9L are also used in the 3.9L 4BT. It's no wonder they live as long as they do, even when being worked 'round the clock.

Reasons for its (Bulletproof) Reputation

Taking a closer look at the nuts and bolts that make up the 4BT Cummins is a great way to help you understand why it enjoys the bulletproof reputation it does. For starters, the parent bore block is cast in gray iron and utilizes a deep-skirt design, meaning that the crankshaft is fully enclosed within the box-like crankcase. The block itself features an integrally cast-in oil cooler cavity, oil pump cavity, and water pump volute. At the front of the block, everything was designed to be gear-driven (no timing belts), including the camshaft, injection pump, oil pump and accessory drive system. Austempered (heat-treated for additional strength), ductile iron helical gears are employed.

Robust Rotating Assembly

Built to withstand the test of time, the forged-steel crankshaft’s fillets and journals are induction hardened for optimum wear resistance and the main caps are secured via 14mm diameter bolts. There are also five main bearings. The connecting rods are forged from steel as well, and each I-beam unit boasts a 1.57-inch diameter, 0.407-inch (10.34mm) thick floating wrist pin in the small end. Its cast-aluminum pistons feature a desirable (and common) keystone top compression ring, and the chilled-iron camshaft resides in the conventional cam-in-block location (for an overhead valve, inline engine) and doesn’t call for press-in camshaft bearings.

Simple, Overbuilt Cylinder Head

Even the cylinder head is an item of overkill on the 4BT Cummins. Simplistic, its two valve per cylinder crossflow design is nothing cutting-edge, but the valve seats are induction hardened to avoid the need for pressed-in valve seats. The ductile iron intake and exhaust rocker arms combine simplicity with high durability and operate on a simple shaft without the need for bushings. Helical intake ports provide high swirl, the exhaust ports are located as far away from water jackets as possible, and six head bolts per cylinder fasten the head to the block. As a result, turbocharger efficiency is never compromised, and head gasket failure is extremely rare.

Mechanical Injection

A straightforward, fully mechanical fuel injection system completes the 4BT Cummins’ simple design. A cam-driven, mechanical lift pump supplies low-pressure diesel to the injection pump, and the injection pump distributes highly pressurized fuel to four pop-off style, mechanical injectors. Three types of Bosch injection pumps are used on the 4BT Cummins: the rotary (distributor type) VE, the inline pump (P-pump) P7100, and the A pump (also an inline pump). Performing a few simple tweaks on the injection pump, courtesy of common hand tools, can unleash substantial performance gains, especially on an engine sporting a P7100.

Common Misconception

It’s often said that industrial 4B and 4BT engines can’t be converted for on-road use. This is inaccurate. While these versions, many of which come from gen-set applications, are typically equipped with a constant-speed injection pump, it shouldn’t keep you from buying that affordable take-out 4BT. Any reputable pump shop can convert the governor section of the pump for variable speed operation (what’s required for on-road use). Turbo location (high or low-mount) is another concern, usually for packaging purposes, but can also easily be rectified with an exhaust manifold flip or swap.

Cummins 4BT Specs

Engine Data

ConfigurationInline 4 Cylinder
Displacement3.9 L, 239 cubic inches
Bore x Stroke4.02 in x 4.72 in
Cylinder HeadCast Iron
Engine BlockDeep-skirt, Cast Iron
Firing Order1-3-4-2
Compression Ratio17.5 : 1 (Most Common)
Injection SystemMechanical, Direct Injection with Mechanical Bosch VE rotary pump (most common), P7100, or a pump
AspirationTurbocharged and non-intercooled (4BT, most common), turbocharged and aftercooled (4BTA), turbocharged and air-to-air intercooled (4BTAA, naturally aspirated (4B)
Valve TrainOHV, 2 valves per cylinder
Weight745-782 lbs with oil
Oil Capacity10 quarts (Most Common)
Governor SpeedVaries with application
Horsepower76 hp @ 2300 rpm (4B) to 140 hp @ 2,500 rpm (4BTAA)
Torque265 lb-ft @ 1600 rpm (Common Early Rating) to 385 lb-ft @ 1,300 rpm
Call Big Bear Engine Company 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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