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A Sinister Sleeper 2008 Ford F-250 With 895 HP

Don’t Let this ’08 F-250’s Murderous Finish Fool Ya!

Jason Sands
May 19, 2015
Photographers: Jason Sands
“Murdering out,” or painting a vehicle completely black, has become more and more popular lately, especially with diesel owners. While the color change does make some trucks look pretty sinister, more often than not, the only performance upgrades a murdered ride may have as support for its mean look are a cold-air intake system, larger exhaust, and a simple handheld programmer.
After taking one look at Clay Stewart’s ’08 Ford F-250, we figured we had his truck pegged. With its leather interior, simple side-exit exhaust, and only an H&S Mini Maxx programmer’s screen providing its gauges, we assumed we were looking at another basic-bolt-on truck…until Clay popped the hood.
Photo 2/15   |   We’re not used to seeing 6.4L Ford-powered trucks sporting big single turbochargers. However, given the horsepower and torque Clay Stewart’s ride puts down, we just might see more of them. With 895 hp and 1,436 lb-ft of torque, Clay’s ’08 F-250 can outrun just about everything on the road.
A whole lot more than just your average 6.4L Power Stroke engine lays under the hood of Clay’s bad-in-black ride. The engine was built to be reliable at near-four-digit power levels. While a 6.4L can make about 550 hp at the wheels with only a PCM tune, Clay’s ’08 checks in at 895 hp—and that’s without such power-adders as nitrous oxide or water-methanol.
Although stock 6.4L long-blocks can handle an immense amount of power, Clay wanted his to be reliable for many years, so he performed a full rebuild at his shop, Stewart Field Services. The block, crank, and rest of the bottom end are stock, but the pistons are coated and de-lipped versions from Midwest Diesel and Auto, as is the camshaft. Pushrods from River City Diesel, valvesprings from Hamilton Cams, and ARP head studs round out a very solid long-block.
Photo 3/15   |   The turbo setup starts with a No Limit Fabrication 5-inch intake designed for high-horsepower 6.4L engines. The chrome unit uses all the stock sensor locations and even includes a pre-filter for longer air filter life.
On the top end of the engine things get interesting, as Clay ditched the factory Ford compound-turbocharger setup for a single 75mm S400 from BorgWarner, which is mounted with a single-turbo pedestal from Maryland Performance Diesel. The exhaust’s hot side isn’t stock, either. It’s comprised of freer-flowing 6.0L manifolds and a River City Diesel up-pipe kit, and a 5-inch downpipe, which Clay built himself.
No Limit Fabrication’s tubes make up the complete intake- and air-discharge sides of the compressor.
While Clay knows he’s pushing the limits of the 75mm turbo’s ability to move air, he also believes the ’charger can help the engine produce the 800 to 900 hp he wants. The stock fuel system, on the other hand, won’t.
Photo 4/15   |   Speaking of turbos, Clay runs a rather large 75mm that features an 87mm turbine to promote exhaust flow, but also a rather tight 0.91 A/R housing that helps with spool-up. Exhaust exits via a 5-inch downpipe Clay built himself.
Clay started this upgrade at the back of the truck, installing a Truck Source Diesel fuel sump, an AirDog 165-gph lift pump, and an Elite Diesel Engineering fuel system, which consists of a fuel bowl delete and a second K16 injection pump, which effectively prevents the common-rails from being drained. Stock injector nozzles certainly aren’t going to cut it, so Clay now uses 100-percent-over nozzles from Midwest Diesel. The final piece of the fuel system puzzle is an H&S Mini Maxx programmer loaded with specially designed tunes from Gearhead Automotive Performance.
With an engine as stout as Clay’s home-brewed 6.4L setup, the rest of the drivetrain is also revamped. With 1,436 lb-ft of torque on tap, the transmission has a heck of a job keeping up. Sparing no expense in this area, Clay uses a Stage V transmission from Elite Diesel Engineering and a 13-inch, 2,200-rpm stall Diesel Performance Converters torque converter that’s matched to the large turbo.
Photo 5/15   |   A stout transmission is needed to handle the nearly 900 hp Clay’s Power Stroke generates. Elite Diesel built a 5R110 automatic with billet input and intermediate shafts, hubs, and a revised clutch count in the transmission. With all these modifications plus a 13-inch torque converter from Diesel Performance Converters, the drivetrain holds up just fine.
The transfer case and driveshafts are factory stock, but the rear axle contains a streetable Detroit Truetrac limited-slip differential by Eaton. To prevent wheelhop and aid traction under hard acceleration, Clay removed the rear blocks and also counts on Precision Metal Fabrication traction bars, American Force wheels, and Nitto tires to keep the truck hooked.
In its first dyno-tuning session, Clay’s F-250 shocked the rollers, putting down 895 hp. The fairly heavy (8,200 pounds) rig is a runner at the track (7.30-second e.t. at 95 mph in the eighth-mile), and Clay also reports that the rig is still very street compliant with the tuning and loose converter. While many diesel pickups out there have mean, “murdered” looks, Clay’s is one that can definitely back it up.
Photo 6/15   |   One of the things that first fooled us about Clay’s deceptive rig is its lack of instrumentation other than a single H&S Mini Maxx. Clay says it gives him everything he needs, including EGT readings as high as 1,750 nerve-wracking degrees. Programming for the Mini Maxx is done by Gearhead Automotive Performance.
Fast Facts:
Year/Make/Model: 2008 Ford F-250
Owner: Clay Stewart
Hometown: Weatherford, Texas
Odometer: 183,000 miles
Engine: 6.4L V-8 Power Stroke; Midwest Diesel de-lipped, coated, and fly-cut pistons; Stage 1 Midwest Diesel camshaft; River City Diesel pushrods; Hamilton Cams valvesprings; and ARP head studs
Fuel: Truck Source fuel sump, AirDog 165-gph lift pump, Elite Diesel Engineering fuel system with twin K16 injection pumps, Midwest Diesel 100-percent-over injector nozzles, and H&S Mini Maxx programmer with Gearhead Automotive Performance tuning
Air: BorgWarner 75mm S400 turbo- charger; Maryland Performance Diesel single-turbo pedestal; and No Limit Fabrication hot-side and cold-side intercooler piping, boots, and 5-inch intake
Exhaust: Ford 6.0L manifolds, River City Diesel up-pipes, custom 5-inch downpipe, and 5-inch straight exhaust
Transmission: Elite Diesel Engineering Stage V automatic transmission and flexplate, and Diesel Performance Converters 13-inch 2,200-rpm stall converter
Horsepower: 895 hp
Torque: 1,436 lb-ft
Tires: 305/45R22 Nitto NT420S
Wheels: 22x10 American Force Rebel SS8
Suspension: Stock, with Precision Metal Fab traction bars, and rear blocks removed
Axles: Stock, with Eaton Detroit Truetrac limited-slip rear differential and 3.73 gears
Fun Fact: Clay has also added a nitrous unit!
Update
Because these rigs never stay the same, Clay sent us some recent photos of a new shiny engine bay right before we went to press. In addition to updating the lift pump to a Velocity 200, he also added a Spearco intercooler, as well as introducing a cool new candy teal blue powdercoat to the valve covers and piping.
Photo 15/15   |   Udgraded 6 4l Power Stroke Diesel

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