Power Wagon 12-Valve Cummins Swap

A 12-Valve Cummins ’49 Power Wagon on 39’s
What happens when you treat the baddest 1-ton 4×4 Classic Dodge truck of all time to a 12-valve Cummins swap, Dana 60 front axle and 14-bolt rear axle, and completely modernize the cab? You get this one-of-a-kind ’49 Dodge Power Wagon owned by Carl Van Rooy. Turning to friend, fabricator, and off-road specialist John Conrad of J.B.’s 4×4, the project took root, got underway, and was ready for delivery 13 months later. In Conrad’s care, he and his crew made the war-born Power Wagon much more than the tractor it essentially was when it left Chrysler’s Warren, Michigan assembly line some 70 years ago.

Restoration & Repower

Cummins P-Pump — While Carl wasn’t necessarily after building a powerhouse, he did have the folks at J.B.’s 4×4 turn up the Cummins’ wick a bit, in the form of a few P-pump tweaks. A bump in timing, higher rpm governor springs, and a custom grind fuel plate increased the P7100’s fueling capabilities, and it feeds a set of remanufactured, stock-spec injectors with fresh nozzles. Combined with the turbo upgrade that was made, the Power Wagon is likely capable of at least 350-rwhp and 700 lb-ft of torque.

The cab-off restoration, powertrain swap, and drivetrain upgrades all took place at Conrad’s Kingman, Indiana facility, with most outsourced work on select components and pieces primarily being performed at local businesses. The Power Wagon’s original frame was powdercoated and modified to accommodate repositioned motor, transmission, and fuel tank mounts, along with relocated leaf spring brackets. PPG provided the base paint that’s about as close to the old Ponchartrain Green as they come.

Making The Cummins Fit

A BorgWarner S300 sits in place of the original Holset HX35W along the exhaust manifold, this SX-E version sporting a forged-milled compressor wheel with a 63mm inducer and a 68mm turbine. The 3-inch, heat-wrapped downpipe just clears the firewall, and all intake and intercooler piping was built in-house at J.B.’s 4×4.

Well known for their ability to convert classic off-road rigs to 6BT or even 4BT power, the guys at J.B.’s 4×4 were definitely up to the task of making a 5.9L fit in the Power Wagon’s narrow engine bay. A set of modified second-gen motor mounts solved the positioning of the Cummins easy enough, but its front-to-back length was the real worry. Stacking all the heat exchangers behind the grille and not having to push the Cummins through the firewall in order to accommodate everything was where Conrad and his crew were most resourceful. The radiator issue was solved by fabricating an aluminum unit in-house, along with an expansion tank which was mounted above the number one cylinder (and between the air intake and cold-side plumbing). Bell Intercoolers supplied the compact air-to-air intercooler that keeps the 12-valve’s EGT in check. An air cleaner from Unique Metal Products also makes for good use of space near the firewall.

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Fresh 5.9L

5.9L Cummins swap — It just fits under the butterfly hood of Carl Van Rooy’s ’49 Dodge Power Wagon, but the 5.9L Cummins is lightyears ahead of the 94hp 230ci flathead I-6 it originally came with. The ’96 model year 12-valve donor was cracked open and refreshed prior to the build, receiving all-new bearings, seals, and a brand-new cylinder head, complete with 60-lb valve springs. The air cleaner assembly is a Unique Metal Products piece, while the expansion tank you see here works in conjunction with the custom radiator, both of which were fabricated by J.B.’s 4×4 in Kingman, Indiana.

Starting with a 470,000-mile running donor, the ’96 model year 12-valve Cummins was torn down for a full-on refresh. The block checked out OK but a crack in the head was all the convincing needed to source a brand-new one, complete with 60-lb valve springs, from Phil’s Automotive Machine Shop in Danville, Illinois. From there, six new stock replacement pistons from Mahle went in, along with fresh bearings, seals, and gaskets from top to bottom. The engine’s fuel system was also renewed thanks to six remanufactured injectors and the P7100 being treated to a considerable advancement in timing, a custom grind fuel plate, and higher rpm governor springs. A 63mm S300 SX-E turbo from BorgWarner handles boost production and spins to life quickly.

Built 47RE & NP205

With its roots running deep in the off-road world, the guys at J.B.’s swapped an open differential Dana 60 in place up front, along with some serious steering upgrades. A custom pitman arm and steering system with PSC cylinder-assist was built, the steering box was relocated and fitted with a high steer arm, and a heavy-duty tie rod assembly was added as well.

Building a 47RE that would never flinch under the load of 700 lb-ft of torque and the strain of turning 39-inch mud terrains, the second-gen-derived four-speed was reinforced throughout, equipped with a RevMax Stage 5 triple-disc converter and high-pressure valve body, and topped off with a Mag-Hytec deep pan. An Anteater Classic STC transmission controller from Firepunk Diesel allowed the guys at J.B.’s 4×4 to dial in the automatic’s shift points, as well as its lockup and Overdrive strategies. Thanks to a first-gen donor, an NP205 transfer case is married to the 47RE, along with an E-brake assembly from Moonshine Mafia Motorsports. Custom length driveshafts from Patterson Driveshaft send power to the front and rear axles.

Dodge Dana 60, GM 14-Bolt

Air Dog — An AirDog fuel supply system mounted along the driver side frame pulls diesel from a custom 35-gallon fuel tank that was fabricated by J.B.’s 4×4. The traction bars, also pieced together at J.B.’s, keep the rear 14-bolt from wrapping and the leaf springs from twisting.

Axle selection boiled down to the tried and true Dana 60 up front and a GM 14-bolt in the rear. Both make use of a 3.73 ring and pinion, but the 14-bolt was treated to a Detroit Truetrac differential, with its axle tubes serving as mounting points for the traction bars that link the axle to the frame. The Dana 60 sits below first-gen intended leaf springs and features a host of steering upgrades. The steering box was relocated and fitted with a high steer arm, a custom pitman arm and PSC cylinder-assist components were added, and a heavy-duty tie rod assembly also made the cut.

The Ultimate Power Wagon

The 14-bolt GM out back conceals a 3.73 ring and pinion and a Detroit Truetrac limited slip differential, both of which sit behind a fabricated diff cover. Its axleshafts are stock and it’s also been converted to employ disc brakes.

The original Power Wagon was known for its simplicity, durability, hauling capability, and off-road readiness, but Carl’s takes things several steps further. The rebuilt P-pumped 12-valve Cummins swap and reinforced 47RE bring million-mile durability to the table. The Dana 60, Truetrac-equipped 14-bolt, 39-inch BFGoodrich Mud Terrains, and 12,000-pound Warn winch provide endless off-road capability. And finally, the show-quality frame, body, and bed restoration—along with the completely refinished and updated interior—make it one of the finest classic repowers we’ve ever come across.