A 1996 Jeep Cherokee built for mud drag racing will use a heavily modified inline-six producing about 434 hp without forced induction. North Carolina-based Newcomer Racing enlarged Jeep’s classic 4.0-liter engine to 5.0 liters and recorded 434 hp on the dyno, more than twice the output of the original Cherokee XJ.
1996 Jeep Cherokee gets a 434-hp naturally aspirated inline-six
The owner wanted an engine that could keep large tires spinning even when thick mud created heavy resistance. In an EngineLabs video, shop owner Keith Newcomer explains that the build needed strong power across a broad rpm range while still pulling hard near the top of the tachometer. That matters in mud racing, where losing wheel speed can quickly stop forward progress.
Newcomer increased displacement by changing both the bore and stroke. The engine now measures 5.0 liters and runs a 13:1 compression ratio while remaining naturally aspirated. Those changes completely alter the character of the original Jeep engine, which earned its reputation mainly through durability and strong low-end torque.
During development, Newcomer tested two fuel-delivery setups. The engine initially ran a carburetor with a custom-built intake before the shop switched to electronic fuel injection. Both configurations produced similar peak-power figures, although the move to EFI also required additional electrical work.
The customer wanted to keep the Cherokee’s original wiring harness, so the shop simplified it by removing connections that the competition vehicle no longer needed. That approach also reduced weight while preserving the basic factory electrical system.
The 434-hp dyno result puts this naturally aspirated five-liter engine 14 hp above the 420-hp Standard Output Hurricane twin-turbo inline-six used as a reference. The comparison only covers peak output, however, since Newcomer built this engine specifically for competition while Stellantis designed the Hurricane for production vehicles.
Newcomer Racing has already pushed another Jeep inline-six beyond 1,000 hp with turbocharging. This project explores how far the engine can go without boost, starting from a design Jeep produced from 1987 through 2006 and that made around 190 hp in the Cherokee XJ.
The larger displacement, high compression and revised fuel system transform the old 4.0-liter engine into something very different from its original role. Instead of powering a conventional off-roader, this version will face the short, demanding acceleration runs of mud drag racing.
