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Cummins QSB and ISB 4.5 L Engine Program

Cummins QSB and ISB 4.5 L Engines for Sale

The 4.5L Cummins is the successor to the famed 4BT (3.9L) engine. This inline-four cylinder diesel power plant is offered in a variety of configurations, but the breakdown begins with the QSB and ISB designations. QSB stands for off-road (i.e. industrial) applications, whereas ISB typically applies to on-road vehicles. It’s common to find the ISB version in buses and step vans, while the QSB found a happy home in telehandlers, generators, skid steers, wood chippers, excavators, tractors, air compressors, and even mining equipment. Overseas (and in particular, Australia), the 4.5L Cummins is a popular diesel swap candidate.

Red Cummins QSB/ISB 4.5 L Engine Front View

Structurally Sound

Like the 4BT, the 4.5L Cummins is based on the use of a cast-iron, parent bore block. However, common misconceptions are that the 4BT and 4.5L share the same crankcase and cylinder head. Neither of these is true. The 4.5L’s deep-skirt block’s casting is very different, and its head is a 16-valve piece rather than 8. However, and similar to how the 4BT shared many of its internal parts with the 6BT, the 4.5L Cummins shares many of its hard parts (such as the connecting rods, pistons, valve springs, head bolts, and even its water pump) with the 6.7L Cummins. In either ISB or QSB form, the 4.5L’s geartrain can be in the front or rear of the engine.

Electronically Controlled

All QSB and ISB 4.5L Cummins engines are electronically controlled. However, some versions were equipped with a VP30 injection pump, a rotary style pump similar in appearance and functionality to the VP44 employed on the ISB 5.9L. These engines can easily be identified by the presence of four individual valve covers. Most QSB and ISB 4.5L’s you’ll come across utilize high-pressure common-rail (HPCR) injection, a 1600 bar (23,200-plus psi) system that provides for better emissions through precise injection events, but that also comes with highly advanced diagnostic capabilities. An added benefit on HPCR versions is that it makes for much quieter engine operation.

Reliable, Efficient, Powerful

In its most potent OEM form, the 4.5L Cummins is capable of producing up to 173 hp and as much as 460 lb-ft of torque (available at 1,500 rpm). Based on its relatively light curb weight (just over 800 pounds), it boasts one of the highest power-to-weight ratios in its class. In fact, the QSB 4.5L is often billed as being comparable to some six-cylinder diesel engines. Couple that with the 4.5L’s proven durability, low NVH, and low cost of operation and you get an industrial engine in high demand.

We build custom solutions for the 4.5L Cummins vs. having surplus stock engines. The configurations are such that having a “one size fits all” solution isn't practical for most customers. If you have a QSB 4.5L engine with a rod though the block or that dropped a valve and needs to be replaced, we have the ability to custom manufacture one back to your original engine serial number (ESN) and CPL.

Cummins QSB 4.5 L Engine Inside a Case Dozer

Cummins QSB 4.5 L in a Case Dozer

The 4.5 L Replacement Engine Process:

1) You provide us with the ESN (engine serial number) and/or CPL (control parts list)
2) You give us as much information on the application as possible
3) You provide us with multiple pictures of the engine to determine how it is dressed
4) Engines are custom manufactured and run-tested
5) Engines are shipped with other build cycles

At Big Bear Engine Company, we often see third party packagers with 3.9L and 4.5L engines from Cummins but with no specific engine serial number present. This is common with Case, International Harvester, New Holland, KCB and Komatsu equipment. Cummins had partnerships with all of those companies to install their engines in those manufacturers’ equipment. These third parties rebranded the engines using their own ESNs. When this happens, we are unable to look up information on a Case or Komatsu engine.

Cummins QSB 4.5 L Engine Data Plate

CASE/Cummins 4.5 L Engine Dataplate

However, if this happens we recommend calling your OEM to determine overall fit (fuel pump, oil pan sump, turbocharger location and flywheel housing size). It is also very important to know the block dimensions and how your specific engine is dressed.

Typical dimensions of the QSB 4.5L engine are 32.2-inches (L) x 28.1-inches (W) x 34.5-inches (H), with a dry weight of 750 pounds (and 817 pounds with oil/fluids). Note that each unit is different, and measurements are approximate estimates based upon Tier II engine data. Tier III and IV engines may be slightly different due to block and ancillary emissions equipment differences.

In cases where the ESN cannot be obtained, we have the ability to manufacture QSB engines back to a few common engine serial numbers. Ultimately, it is up to the customer to determine the proper fitment of the engine for their application.

Common Front Gear Train QSB 4.5 ESNs we build to are:
ESN: 30689695 CPL: 8401
ESN: 720111544
ESN: 46376515

QSB and ISB 4.5 L Long Blocks for Sale:

ISB 4.5 L Long Block Front View


• Block
• Cylinder Head
• Camshaft and Lifters
• Crankshaft
• Connecting Rods
• Rocker Assemblies
• Gaskets, Rings, Seals, Bearings
• Timed Front Gear Group
• Oil Pan and Pickup Tube
• Standard 12 Months Parts Replacement Warranty
• 1 and 2 Year Parts/Labor Extended Warranties also Available

Note: Long blocks with sometimes come with the front cover and gear housing already configured to your specific fuel pump. Other times, you will have to reuse your old gear housing and front cover off of the old engine.

QSB and ISB 4.5 L Extended Long Block Engines for Sale:

Our replacement extended long block 4.5L ISB and QSB engines are built back to your ESN and CPL. Extended long blocks are roughly a 75-percent finished assembly built with 90-percent OEM parts and 10-percent aftermarket parts, when available. That being said, variations may exist from engine to engine. A general guide is that replacements will include the fuel system, turbocharger (unless naturally aspirated) and oil pan. Usually customers will reuse starters, alternators, flywheels, flywheel housings (SAE #1, #2 or #3) as they are unlikely to be damaged during an engine failure. Engines do not come with wiring harnesses, power steering or vacuum pumps, motor mounts, or transmission adapter plates. Note that we also have the ability to build QSB 4.5L power units with the muffler, radiator, and control panel if needed. ECM’s are programmed before they are shipped if the customer has the ECM code number and/or part number. Each configuration is different, but most QSB or ISB 4.5L extended long block engines come with:

• Block
• Cylinder Head
• Camshaft and Lifters
• Crankshaft
• Connecting Rods
• Rocker Assemblies
• Gaskets, Liners, Rings, Seals, Wrist Pins, Bearings
• Injectors
• Oil Cooler
• Oil Filters
• Intake and Exhaust Manifolds
• Housings (Front and Rear)
• Brackets and Pullys
• Fuel Injector Pump
• ECM (Programmed if Customer Has ECM Code)
• Turbo
• Oil Pan and Pickup Tube
• Standard 12 Months Parts Replacement Warranty
• 1 and 2 Year Parts/Labor Extended Warranties also Available

Cummins 4.5 L Specs

Engine Data

ConfigurationInline 4 Cylinder
Displacement4.5 L, 275 cubic inches
Bore x Stroke4.02" x 4.39"
Cylinder HeadCast Iron
Engine BlockCast Iron
Emissions RatingTier II-IV
Compression Ratio17.2:1
InjectionDirect Injection, High Pressure Common Rail
AspirationHolset Turbocharged, Intercooled
Valve TrainOHV, 2 valves per cylinder
Weight817 lbs. Dry
Cooling Capacity11.6 quarts oil, 9 quarts of coolant
Governor SpeedVaries with application
Horsepower110 -170 HP @ 2500 rpm
Torque360 -459 lb-ft @ 1500 rpm
Give us a call today at 844-340-4114 for immediate sales and support for the Cummins 4.5L , 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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