Jeeps are known for their reliable performance, albeit at a gradual pace. Tuners have recently found that these robust engines can generate significant power with forced induction; however, one shop successfully achieved higher output than several variants of the modern Hurricane inline-six without the use of forced induction.
This shop is Newcomer Racing, located in North Carolina, which previously pushed a Jeep inline-six past 1,000 horsepower using turbocharging and carburetion. In this particular build, the engine produces 434 horsepower, which, notably, is achieved without the aid of a turbocharger or supercharger to force additional air into the combustion chambers. This output also exceeds the standard-output variant of the Hurricane inline-six used in the Grand Wagoneer by 14 hp.
EngineLabs details in a video how Newcomer accomplished this feat with an engine bored and stroked to 5.0 liters and a 13:1 compression ratio. The build was tailored for a client wanting to engage in “mud drag type stuff” with a 1996 Cherokee, explains Keith Newcomer, the owner of Newcomer Racing, in the video. The client desired a broad power band to maintain wheel speed while driving large tires through muddy terrain, coupled with a good mix of torque and high-end power.
Initially built with a carburetor and a custom intake arrangement, Newcomer later transitioned to EFI. The customer wanted to retain the stock wiring harness from the Cherokee, so Newcomer removed all non-essential components, shedding a few pounds in the process. Both setups yielded similar peak power—over two times the 190 hp generated by a stock 4.0-liter inline-six in a new XJ Cherokee.
Dyno Testing A Killer N/A Jeep 4.0L With Newcomer Racing — Carb Vs. EFI | EngineLabs BUILDS
The 4.0-liter inline-six was produced by Jeep from 1987 to 2006, utilized across its various models during its extensive lifespan. It gained fame as, to borrow a phrase from my colleague Caleb Jacobs, “a tough-as-nails truck engine” that prioritized reliability and low-end power over sheer horsepower. That level of performance was widely accepted from a Jeep throughout most of the engine’s tenure. The first performance-oriented Jeep—the WK Grand Cherokee SRT8—debuted with Hemi V8 power in 2006, just as the inline-six was being phased out.
Witnessing an atypical engine modification like this is always exciting. The Jeep inline-six was initially designed contrary to performance engines, yet its robust design proves it to be an excellent base for high-power modifications. Achieving this power without forced induction makes the accomplishment even more remarkable.
**Transformation of Legendary Jeep 4.0L Engine with Extra Liter of Displacement Yields Notable Power Boost**
The Jeep 4.0L engine, praised for its robustness and off-road prowess, has been a favorite among car enthusiasts since its launch in the early 1980s. This inline-six engine is celebrated for its dependability and performance, establishing itself as a mainstay in various Jeep models. However, as automotive innovations advance, numerous enthusiasts look for ways to enhance the performance of this legendary engine. One of the most potent modifications is expanding the engine’s displacement by one more liter, resulting in a substantial power boost.
### Grasping Engine Displacement
Engine displacement signifies the cumulative volume of all the cylinders within an engine. It is generally expressed in liters (L) or cubic centimeters (cc). Displacement is a pivotal element in determining an engine’s power output, as a greater displacement permits a larger volume of air and fuel to be combusted, thereby leading to improved horsepower and torque.
### Overview of the 4.0L Engine
The Jeep 4.0L engine is a sturdy power source that generates around 190 horsepower and 235 lb-ft of torque in its factory configuration. It is equipped with a cast-iron block and aluminum cylinder head, providing a strong basis for modifications. The design of the engine includes a lengthy stroke and a comparatively high compression ratio, which enhances its torque delivery, particularly during off-road driving.
### Displacement Enhancement: The 5.0L Conversion
To realize a notable power increase, many enthusiasts choose to boost the displacement to 5.0L (or 5000cc). This can be achieved through several methods, including:
1. **Boring and Stroking**: This process enlarges the cylinder bores and extends the stroke length. By increasing the bore size, more air and fuel can be drawn in, while a longer stroke contributes to a larger combustion chamber volume.
2. **Upgraded Components**: Alongside increasing displacement, it is crucial to enhance components like pistons, crankshafts, and connecting rods to withstand the additional power and strain on the engine. Forged parts are often recommended for their durability and strength.
3. **Improved Fuel and Air Supply**: To accommodate the increased displacement, modifications to the fuel delivery system (such as larger injectors and upgraded fuel pumps) and air intake (like high-performance air filters and intake manifolds) are indispensable. This ensures optimal air-fuel mixture for effective combustion.
### Performance Improvements
The resulting power gains from escalating the displacement from 4.0L to 5.0L can be significant. Enthusiasts have reported increases of 50-100 horsepower, contingent on specific modifications and tuning. The torque increase is frequently even more noticeable, leading to enhanced acceleration and superior off-road capability.
### Tuning and Engine Management
Following the enlargement of the engine’s displacement, proper tuning is vital to maximize performance and maintain reliability. Upgrading the engine management system or using a standalone engine control unit (ECU) enables precise modifications to fuel maps, ignition timing, and other parameters. This tuning process is crucial for accommodating the new airflow and fuel delivery traits of the modified engine.
### Closing Thoughts
Modifying the iconic Jeep 4.0L engine by boosting its displacement to 5.0L provides substantial power and torque gains, elevating the overall driving experience. With the right mix of components, tuning, and meticulous attention to detail, Jeep enthusiasts can unlock the complete potential of their engines, making them even more proficient on and off the road. As is the case with any performance upgrade, balancing power, reliability, and drivability is essential to achieving optimal results.