There’s no denying that we all want big horsepower on tap, and that we want it available at all times. The more the better. But keeping a high-powered diesel alive can be a challenge, especially when the engine is exposed to triple-digit boost, excessive cylinder pressure, and the transmission needs to survive in an 8,000-pound truck. If you want reliability while making four-digit power, the truck’s weak links must be addressed from top to bottom or you’ll never be able to keep it on the road long enough to enjoy it. A built engine, big fuel, lots of air, and a stout transmission are among the essentials. And while big horsepower and rock-solid durability don’t come cheap, you can’t exactly put a price tag on peace of mind, either.

With the goal of transforming a low-mile ’06 F-350 into a powerful yet reliable play toy, Randy Romans brought his Super Duty to Fleece Performance Engineering in Brownsburg, Indiana, to get the best of both worlds. Under Fleece’s care, the truck’s problematic 6.0L Power Stroke was ditched in favor of a 6.7L-based Cummins sporting big compound turbos, dual CP3s, and massive injectors, with the engine ultimately being bolted to a full billet 48RE automatic transmission. Along the way, several mandatory driveline mods were needed, traction bars were added, and custom-tailored engine and transmission tuning made for a very street-friendly truck capable of making upwards of 1,200 rwhp.

Join us for an in-depth look at Romans’ tire-shredding Super Duty, where we’ll spell out all the upgrades that were necessary to make his F-350 both reliable and drivable at this power level.

Thanks to the handywork of Jake Richards, Fleece Performance Engineering’s lead technician, the engine bay of Randy Romans’ ’06 F-350 appears as if it was born to house the 6.2L Cummins it currently does. When we say 6.2L, we’re referring to the truck’s competition-caliber engine built by Freedom Racing Engines—the machine shop arm of Fleece’s Indianapolis-area operation. Based on an ’09 6.7L block, the cylinders are sleeved down and a piston close in size to a 0.040-inch-over 5.9L unit is run. In this engine’s case, a set of Mahle Monotherm pistons is being utilized (made from forged steel and designed for extreme abuse). A factory 6.7L crankshaft is used in conjunction with custom-length rods from Wagler Competition Products.
You’re looking at the smaller, high-pressure charger in Romans’ compound arrangement—if you can call a T4-flanged S475 small. The Fleece-built charger possesses a billet compressor wheel, an 87mm turbine wheel, and a 0.90 A/R exhaust housing. Below the S475 and closer to the firewall you’ll find a BorgWarner S488 SX-E serving as the low-pressure unit. The big atmospheric charger sports an 88mm inducer, forged milled compressor wheel (FMW), a 96mm turbine wheel, a 1.32 A/R exhaust housing with a T6 flange, and a 360-degree thrust bearing for durability. The two windmills combine to make 85 psi of boost in a conservative tune, while more aggressive tunes can easily peg 100 psi. Compressed air is forced through a Banks Techni-Cooler intercooler on its way to the head. All piping required to make the compound system work was built in-house at Fleece by Jake Richards.
One holdover part intended for the 6.0L Power Stroke but made to work with the Cummins is this aluminum coolant reservoir from PSP Diesel. Made from 5052 aluminum and TIG-welded to perfection, the reservoir features a glass window for monitoring coolant level and a 1/8-inch bung for a coolant pressure sensor, and it bolts directly in place of the plastic (easily cracked) OEM unit. Aluminum construction allows it to double as a heat sink to help keep coolant temps down.
Complementing the ported Performance Street cylinder head from Freedom Racing Engines is a Big Hoss intake manifold from Gale Banks Engineering. The folks at Freedom have found the Big Hoss manifold to be one of the best-performing off-the-shelf units in the diesel aftermarket, and they include it on many street engines. On top of the flow increase the Big Hoss provides, it also offers uniform air distribution into each cylinder—which means more power on tap at any boost level. On the opposite side of the worked-over head you’ll find a Steed Speed T4-foot, twin-turbo exhaust manifold.
To achieve the four-digit power figure Romans was after, big fuel mods were in store. A dual CP3 kit from Fleece is employed to keep plenty of rail pressure on tap for a set of 200% over S&S Diesel Motorsport injectors. A Fleece PowerFlo 750 pump is mounted in the factory location along with a second belt-driven unit (shown here). Both CP3s are 10mm stroker pumps, each capable of supporting 800 rwhp on its own.
Keeping the stroker CP3s well-fed is a FASS Signature Series fuel system mounted along the driver-side frame rail. Capable of flowing 290 gallons per hour, this system can support between 1,200 and 1,500 hp. Supply pressure holds steady between 16 and 18 psi.
The goal of building an immensely powerful truck with great street manners is nothing more than a pipe dream without good engine tuning. As for ECM calibration, Oz Tuner got the call and created five custom tunes built specifically for Romans’ fuel and air combination. As a result, the truck is extremely drivable with the big yet properly sized chargers quickly coming to life and cleaning up any smoke.
Because the combination of big torque production and a heavy truck is the quickest way to break transmission parts, the guys at Fleece decided to place a proven slushbox behind the 6.2L Cummins: a competition 48RE from SunCoast. With billet input, intermediate, and output shafts, a billet direct and forward drum, custom frictions, Kolene steels, and an application-specific valve body, the four-speed automatic is equipped with the very best components SunCoast has to offer. A billet-stator, triple-disc torque converter tops things off and—along with tuning—makes the big turbos very drivable.
With Oz Tuner making the engine run like a top by way of EFI Live software, the 48RE’s operation was fine-tuned via Powertrain Control Solutions’ transmission software and a TCM-2800 controller. Richards handled dialing-in of the built automatic’s shift points, shift firmness, and converter lockup.
Use of a Dodge NV273 transfer case allowed Richards to scrap the truck’s factory two-piece rear driveshaft in favor of a one-piece unit from a Ram. With help from nearby Accurate Driveline and Machine, the OEM Ford front shaft was converted to work in conjunction with the transfer case. Richards also built a custom transmission cross member for added support.
On a previous visit to Fleece Performance Engineering’s Brownsburg, Indiana, headquarters for other business, we snapped a shot of Romans’ Super Duty when it was under the knife. Here you can see the SunCoast 48RE mocked up, bolted to the NV273 transfer case, and the heat-wrapped downpipe ready to be clamped to the back of the atmosphere turbo. At this point in the project the Comp 6.2L Cummins was being buttoned up across the street at Freedom Racing Engines.
To properly expel spent exhaust gases, a 5-inch-diameter exhaust system from Jamo Performance Exhaust was bolted in place. Made from T-409 stainless steel, the conventional-exit system features a free-flow muffler and a 5×6-inch polished stainless tip.
It pays to know the status of key vitals at all times when you’re working with four-digit horsepower. With a quick glance at the A-pillar, Romans can check in on fuel supply pressure being delivered to the CP3s, EGT at the exhaust manifold, overall/combined boost pressure, and transmission temperature, thanks to an AutoMeter quad pod fitted with Sport-Comp II series gauges.
With just 85,000 miles’ worth of seat time, the Lariat interior is in supreme condition despite the truck’s 13 years of age. Perhaps the best news in the interior is that the tap-shift functionality of the ’08-and-newer style gear shift lever is fully viable.
Beyond the truck’s full billet transmission, 1480 series U-joints, and other reinforcement measures, a set of traction bars was mandatory to keep the rear 10.5 axle from wrapping and its leaf springs from twisting. A pair of 1.5-inch-diameter, 0.095-inch-wall chromoly tubes link the axle to the frame via ¼-inch-thick weld-on mounts.
On any engine that’s exposed to elevated boost and cylinder pressure, you’re inevitably going to have some blowby. This remote-mount oil catch can from Moroso makes use of a filtered breather that traps oil while allowing air to escape, and also features a drain valve to simplify drain intervals.
For a level stance, 2-inch coil spacers exist up front. The added height provides ample clearance for the 33×12.50R20 Toyo Open Country M/T and 20×12 Fuel Off-Road FF71 wheel/tire combination Romans runs.


Romans no longer tows with his F-350 since he has other trucks for that—but he could if he wanted to. After all, thanks to a well-spec’d compound turbo arrangement, spot-on tuning, good head flow, and the Banks Techni-Cooler, he rarely sees more than 1,300 degrees on the pyrometer when cruising around empty. Smart driving could easily make moving lighter loads more than plausible.
Surprisingly, the factory, 3.73-geared Ford 10.5-inch rear axle (or the stock front Dana 60) has yet to give Romans any problems. However, he hasn’t ruled out the possibility of adding stronger axle shafts or a locker in the future.
We’re all about the de-badged, clean-look on a healthy-running street truck. But with so much work put into it, it was hard for Romans not to splurge a little. These under-the-radar badges offer a hint as to what the Ford is packing under the hood. However, we doubt anyone would suspect this “funny sounding” Super Duty is turning out well north of 1,000 hp.
Though it may look like just another truck on the job site, Romans’ fire-breathing Cummins is easily sending 1,250 rwhp to the pavement according to the folks at Fleece. Even though horsepower beyond 1,000 rwhp proved unattainable on the chassis dyno due to too much tire spin, the truck’s rolling four-wheel drive burnouts sure make its 1,200+ power figure believable. How many 8,000-pound trucks do you know of that can blow off all four tires between 30 and 65 mph?

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