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

Big Bear Engine Company Warranty SealExperience the power of diesel! Our Cummins 4BT Engines are the best in the business. Whether you are looking to replace small industrial equipment, researching your next crate engine, or are looking to upgrade to diesel through a 4BT Jeep Swap, we can get you up and running. The Cummins 4BT is a workhorse in its own right offering torque when you need it and the durability to run at full load for extended periods of time.

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

4BT Long Blocks:

Cummins 4BT Surplus EngineOur 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%-75% of a complete engine build. Think of it as the "guts of the engine" but nothing dressing it out. To educate customers specifically about long blocks we have created a 4B long block informational page here. Note, we also offer Cummins 4BT engine 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% parts failure rate. As a guide, a component build is about 90% OEM parts and 10% 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% 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 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
AERA Association Member• Oil Pump and Water Pump
• Oil Cooler
• Oil Filters
• Intake and Exhaust Manifolds
• Housings (Front and Rear)
• Brackets and Pulleys
• Fuel Injector Pump
• Timed Front Gear Group
• Valve Cover
• Turbo
• Aftercooler (only on some models)
• Air Compressor (only on some models)
• New Rear Sump Oil Pan and Pickup Tube
• Standard 12 Months Parts Replacement Warranty
• 1 and 2 Year Extended Parts/Labor Warranties also Available

4BT Engine Models:

• 4B 76 HP - (Inline A Pump)
• 4BT 105 HP - (Inline A Pump)
• 4BTA 130 HP - (Inline A Pump)
• 4BTAA 140 HP - (Rotary or P-7100 Fuel Pumps)

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 only 105 hp at 2,300 rpm, but however the engine is extremely popular when it comes to its torque ratio. The 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 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 in addition to being the biggest diesel engine that's 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. While its simplistic, two valve per cylinder crossflow design is nothing cutting-edge, 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’ simplistic 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 a few common hand tools, can unleash substantial performance gains, especially on an engine sporting a P7100.

Cummins 4BT Specs

Engine Data

Configuration Inline 4 Cylinder
Displacement 3.9 L, 239 cubic inches
Bore x Stroke 4.02 in x 4.72 in
Cylinder Head Cast Iron
Engine Block Deep-skirt, Cast Iron
Firing Order 1-3-4-2
Compression Ratio 17.5 : 1 (Most Common)
Injection System Mechanical, Direct Injection with Mechanical Bosch VE rotary pump (most common), P7100, or a pump
Aspiration Turbocharged and non-intercooled (4BT, most common), turbocharged and aftercooled (4BTA), turbocharged and air-to-air intercooled (4BTAA, naturally aspirated (4B)
Valve Train OHV, 2 valves per cylinder
Weight 745-782 lbs with oil
Oil Capacity 10 quarts (Most Common)
Governor Speed Varies with application
Horsepower 76 hp @ 2300 rpm (4B) to 140 hp @ 2,500 rpm (4BTAA)
Torque 265 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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