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A 600-PLUS HORSE ’97 F-250 ON SUPER DUTY AXLES

Forty thousand miles in 14 years. Yeah, you could say Andy Inman’s ’97 F-250 is his “baby.” The ultra-clean OBS Ford is a rare gem in a world where these trucks are getting harder and harder to find—and the fact that it sports late-model Super Duty axles and suspension makes it even more unique. But this square-bodied beauty packs more than late-model running gear—the 7.3L Power Stroke under the hood cranks out roughly four times the power it did when it left the factory.

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Aside from a set of Comp Cams 910 springs, Smith Brothers chromoly pushrods, and ARP head studs, the 7.3L Power Stroke in Andy Inman’s ’97 F-250 is completely stock. Thanks to an Irate Diesel Performance T4 turbo mount, intercooler pipes (powdercoated “Colin Orange”), and 3-inch intake plenums, the 154,000-mile 7.3L makes the most of using an S400 frame turbocharger in the valley.

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The S476 BorgWarner turbo features a 76mm compressor wheel (inducer), a street-friendly 83mm turbine wheel (exducer), and a 1.10 A/R exhaust housing. At full tilt, the charger produces 55 psi of boost for the forged-rod V8 to ingest. An aluminum intercooler out of a 7.3L Super Duty keeps EGT in check.

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Keeping the 300/200 hybrids supplied with plenty of diesel is this restriction-free, competition fuel system from Irate Diesel Performance. The race-ready system employs a top-of-the-line 41401 Fuelab lift pump and pulls fuel from a Beans Diesel Performance sump in the tank.

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Keeping both performance and reliability in mind, Inman chose to meet the hydraulic demands of his Unlimited Diesel Performance 300/200 injectors with a dual high-pressure oil pump system from Full Force Diesel. A DieselSite Adrenaline HPOP resides in the factory location, while a re-manufactured Bostech unit dwells just above it.

The Score

Back in 2003, Inman was eager to build a ’94.5-97 Ford. His one stipulation was that it had to be a short-bed model with a solid front axle—a truck Ford didn’t build during this era. Opting to swap a Dana 60 under a ¾-ton rather than perform a short bed conversion on an F-350, Inman purchased his crew cab F-250 in bone stock form and with 113,000 miles on the odometer. Almost immediately, he had the Dana 50 TTB on the scrap pile and a Dana 60 in place. A 4-inch BDS Suspension lift and 35-inch mud terrains would follow.

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To withstand upward of 1,200 lb-ft of torque, Inman turned to friend Chuck Dorsey of Dorsey Diesel for a bulletproof transmission. Inman would receive one of Dorsey’s Stage 3 E4ODs, complete with a billet input shaft, modified pump and valve body, GPZ clutches, and a Torque Converter Technology triple-disc converter. Added insurance comes by way of a Super Duty transmission cooler, and shift points can be controlled manually thanks to a custom shift box from Irate Diesel Performance’s Matt Maier.

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After years of sporting a solid front axle, 4-inch lift, and leaf springs at all four corners, Inman decided to change things up a bit this past spring. Up front, the leaf-sprung Dana 60 would go by the wayside in favor of a Dana 60 out of an ’08 Super Duty, complete with coil springs and radius arms. And even though a Super Duty axle swap sounds in-depth to the layman, Inman convinced us it was extremely straightforward. “It’s more about taking measurements and drilling holes than anything else,” he tells us. “And the radius arm brackets go all the way up to the front body mounts, so you can’t screw that up.”

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Adding a coil spring, radius arm front suspension to an old body style Ford results in a night and day difference in ride quality. A set of 2.0 Performance Series IFP Fox shocks—spec’d by BDS Suspension to work seamlessly in Inman’s unique application— complement the coil spring front suspension.

600+ HP 7.3L

After living in the 400rwhp range for several years— courtesy of a set of 160/30 injectors, an electric fuel system, and a Dominator 66 drop-in turbo—Inman has since upped the ante considerably. While the factory forged-rod bottom end is still being utilized, 300cc, 200% nozzle hybrid injectors from Unlimited Diesel Performance now sit above each cylinder. Inman stepped up his high-pressure oil game as well, in the form of Full Force Diesel’s dual high-pressure oil pump system. A full competition fuel system from Irate Diesel Performance ensures plenty of diesel is always on tap for the hungry injectors.

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CFM Increase

Allowing the 7.3L to breathe better, Inman installed a T4 turbo mounting kit from Irate Diesel Performance, complete with 3-inch intercooler pipes and intake plenums. His turbo of choice was a 76mm BorgWarner S400 that was built with street-ability in mind but that could support north of 650 rwhp if Inman needed it to. The truck’s exhaust begins with a 3-inch Irate downpipe and transitions into a fully-welded 5-inch Diamond Eye system.

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Also sourced from an ’08 Super Duty, a 10.5 Sterling replaced the factory 10.25 axle out back, along with its respective leaf springs. To achieve the stance Inman was after, 3-inch blocks are utilized. Also notice the Ford Bronco tank, which allowed him to do away with the factory saddle tanks and (more importantly) the restrictive fuel selector valve when it came time to run the aforementioned high-fl ow fuel supply system from Irate Diesel Performance.

Stage 3 E4OD

For the transmission to handle upward of 1,200 lb-ft of abuse, Inman turned to nearby Dorsey Diesel for one of that company’s Stage 3 E4ODs. Incorporating a Torque Converter Technology triple-disc converter, billet input shaft, GPZ clutches, and a modified pump and valve body into the build, the four-speed automatic is fitted with arguably the best aftermarket components you can buy. Along with the transmission, Dorsey Diesel took care of all the truck’s custom tuning needs (available via a Hydra Chip from Power Hungry Performance). So far, a conservative 2.6 millisecond tune allowed Inman’s F-250 to clear 626 hp and 1,187 lb-ft on the chassis dyno.

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While the 10.5-inch ring gear Sterling axle was a slight upgrade over the factory 10.25 unit, Inman knew it would still be susceptible to torrential axle wrap with the power he planned to make. To keep the axle from rotating and the leaf springs from twisting, he had nearby Tube Works Fabrication in Desloge, Missouri, build a set of stout traction bars. The bars attach to both the frame and axle via welds.

’08 Axles & Suspension

Most recently, Inman improved the ride quality of his OBS tenfold by adding a set of ’08 Super Duty axles and suspension. Thanks to the help of friend, Johnny Pettus, the Dana 60 and its respective coil spring, radius arm front suspension was underneath the truck in two days’ time. While most of the steering components from the ’08 donor swapped over, an ’05 steering box was sourced and an adjustable track bar from BD Diesel was added. An ’08 rear Sterling 10.5 and leaf springs would also be installed, replacing the factory 10.25 unit. Thanks to the Super Duty axles and top-of-the-line performance parts, Andy Inman has effectively ushered his ultra-clean OBS into the modern age—an era where ride comfort and big horsepower go hand-in-hand.

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With just 154,000 miles on the odometer and an owner who’s very particular about his truck, Andy Inman’s ’97 is as clean as it gets in the cab. Aside from the stereo and NV series Auto Meter gauges along the driver side A-pillar (EGT, trans, boost), the interior is all original.

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It only makes sense to call attention to the fact that your old body style is sporting an 8x170mm lug pattern, right? Inman scored these factory 20-inch wheels off of a ’15 King Ranch and wrapped them in 305/55R20 Nitto Terra Grappler tread.

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Following a soft launch on a conservative tune, Inman’s OBS has run a low 8 at 83 mph in the eighth-mile so far. However, with more aggressive tuning on the way and more time behind the wheel, we wouldn’t be surprised if the truck ended up running 7.70s like clockwork.

“THANKS TO THE SUPER DUTY AXLES AND TOP-OF-THE-LINE PERFORMANCE PARTS, ANDY INMAN HAS EFFECTIVELY USHERED HIS ULTRA-CLEAN OBS INTO THE MODERN AGE.”

In the process of combining old school looks with a plusher ride and respectable horsepower, Inman managed to build a work of art that’s also a blast to drive. And given that Inman performed all the work at his own facility, Andy’s Garage in Park Hills, Missouri, he has the satisfaction of saying the truck is owner-build. DW