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Before today’s Hurricane twin-turbo engine, a simpler 4.0-liter inline-six powered countless Jeeps reliably but slowly. Tuners have since discovered that these stout engines can make big power with boost, but one shop managed to make more power than some versions of the current Hurricane inline-six without forced induction.
The shop in question is North Carolina-based Newcomer Racing, which previously took a Jeep inline-six all the way past 1,000 horsepower with turbocharging and carburetion. This build only produces 434 horsepower, but again, that’s without the benefit of turbos or a supercharger to cram more air into the combustion chambers. And it’s 14 hp more than the standard-output version of the Hurricane inline-six that currently powers the Grand Wagoneer.
EngineLabs via YouTube
As described in a video from EngineLabs, Newcomer achieved that with an engine bored and stroked to 5.0 liters and running a 13:1 compression ratio. It was built for a customer who wants to do “mud drag type stuff” with a 1996 Cherokee, Newcomer Racing owner Keith Newcomer explains in the video. The customer wanted a wide power band to keep wheel speed up while churning big tires through the mud, with a good balance of torque and top-end grunt.
Newcomer originally built the engine with a carburetor and custom intake setup, but switched to EFI. The customer also wanted to keep the Cherokee’s stock wiring harness, so Newcomer stripped out everything not related to basic functions, saving a few pounds in the process. Both setups produced similar peak power—more than double the 190 hp a stock 4.0-liter inline-six would have made in an XJ Cherokee when new.
Dyno Testing A Killer N/A Jeep 4.0L With Newcomer Racing — Carb Vs. EFI | EngineLabs BUILDS
Jeep manufactured the 4.0-liter inline-six from 1987 to 2006, using it throughout its lineup during that very long lifespan. It became iconic as, to quote my colleague Caleb Jacobs, “a down-and-dirty truck engine” that emphasized reliability and low-end grunt over raw horsepower. That was all anyone expected from a Jeep during most of this engine’s production run. The first performance Jeep—the WK Grand Cherokee SRT8—arrived with Hemi V8 power as a 2006 model, just as the inline-six was heading toward the door.
It’s always cool to see an unusual engine build like this. The Jeep inline-six was designed as the opposite of a performance engine, but its sturdy construction actually makes it a good foundation for a big-power build. Getting that power without forced induction makes this build all the more impressive.
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Stephen has always been passionate about cars, and managed to turn that passion into a career as a freelance automotive journalist. When he’s not handling weekend coverage for The Drive, you can find him looking for a new book to read.
