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UNLIMITED DIESEL PERFORMANCE’S P-PUMPED 7.3L PULLER

Ah, the rare gem that is the P-pumped 7.3L. It’s an engine combination born out of both necessity and loyalty. Folks that blaze this trail know it’s mandatory to scrap the HEUI injection system in order to be competitive, and their unshakable devotion to the 444-cubic-inch V8 keeps them from veering away from their Ford/Power Stroke roots. Such was the case for Ben Burnworth and Nate Bailor, avid truck pullers who happen to own Unlimited Diesel Performance in Bremen, Ohio. After campaigning a HEUI-fi red 7.3L for years, the competition kept pulling away from their bull-nose Ford and both of them knew it was time for a change. “It was basically a 600hp truck at the time, and that was with compound S400s,” Bailor tells us. “It was doing good for a 7.3L, but wasn’t where we needed to be to run with the rest of the class.”

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Trials & Tribulations

After hatching a plan to go mechanical, Bailor and Burnworth quickly learned that they were essentially on their own. Unlike with the Cummins camp, there is no set precedent as to what makes a mechanically injected 7.3L both competitive and dependable. As a result, a lot of trial and error lay ahead. Torched pistons, cracked heads, and turbo rule changes all literally threw wrenches into their plans at one point or another. In the end, it was all part of an extensive learning curve that led to the current parts combination, which has proven rock-solid reliable.

Block & Crank: The Only OE Parts

Aside from its retention of the factory block (which is fi lled with Hard Blok) and crankshaft (which is internally balanced), the engine is a one-off work of art. A Hypermax bed plate eliminates the main cap walk the 7.3L is known for, and provides significant reinforcement for the crankcase. R&R Racing Products’ forgedsteel rods attach to 0.010-inch over, forged-aluminum FSR pistons from D&J Precision Machine, and a camshaft spec’d by Bob Holmes highlights the short-block’s key hard parts. A set of solid, re-cast cylinder heads from D&J Precision Machine represent the most exotic cast-iron 7.3L heads we’ve ever seen. They’re fireringed and graced with massive intake valves, Jesel roller rockers, 9/16-inch ARP studs, and they incorporate International-style, mechanical injectors.

The Inline Eight

Front and center in the lifter valley sits a worked-over, 13mm inline eight cylinder Bosch P7100 from Northeast Diesel Service. A billetaluminum front cover designed and machined by D&J Precision Machine accommodates the big P-pump, while a Waterman lift pump coupled to back of the R&R dry sump oil pump supplies 50psi worth of fuel pressure. Custom-bent injection lines branch out to International-based, dual-feed, billet-body injectors from Scheid Diesel.

A Properly Vetted Turbo

With eight cylinders and more than 440 cubic inches to feed, smooth-bore turbo rules have definitely muffled the power potential of this engine. But with the rules being what they are, Bailor and Burnworth had no choice but to exhaust every avenue to find the right charger. After spending countless hours on the engine dyno—which included the vetting of some of the best 3.0-inch smooth-bore turbos on the market—they settled on a unit from Columbus Diesel Supply. The Holset-based charger produces 50 psi of boost under peak load, but spins an incredible 130,000 rpm while doing it. When combined with a PT4000 Precision Turbo & Engine intercooler, the engine produces roughly 1,100 hp, 1,800 lb-ft of torque, and never sees EGT crest 1,600 degrees.

Open Driveline

A four-disc Crower clutch, Pro Fab Machine reverser, and Pro Fab drop box provide the necessary links in the chain for getting as much of that 1,100 hp to the ground as possible. Final power transfer takes place in the form of a Rockwell 20-145 axle out back and an upgraded Dana 60 up front. Six BFGoodrich All-Terrains, aboard 16×12- inch aluminum Real Racing wheels, are tasked with grabbing hold of the track.

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Well-Oiled Machine

With their engine issues behind them and an overall setup that’s become predictable, Bailor and Burnworth were able to put together a successful season in 2017. Despite being underpowered, they finished third in points in their local 7,800-pound Limited Pro Diesel class along the Central Ohio Truck Pull Circuit. At non-sanctioned events, it’s not beyond them to crank the P-pump up to 800cc, run a 4.1-inch turbo, and carry 5,800 rpm down track (compared to its typical 4,200 rpm sprints). No matter the venue, the P-pump 7.3L-powered ’81 Ford campaigned by Unlimited Diesel Performance is sure to continue turning heads wherever it competes.DW

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Underneath the billet-aluminum intake manifold and valve covers, an OEM cast-iron block serves as the foundation for Unlimited Diesel Performance’s P-pumped 7.3L monstrosity. After its water jackets were filled with concrete, Fowler Engines bored the cylinders 0.010-inch over and machined the deck surface to accept fire rings, which protrude into both the block and heads. An internally balanced, factory-based crankshaft is anchored in place via a Hypermax bed plate, and it swings a set of R&R forgedsteel rods connected to fly-cut FSR pistons from D&J Precision Machine. A custom-profile camshaft designed by Bob Holmes kickstarts the big V8’s efficient valvetrain operation.

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To both improve durability and optimize the location of the mechanical injectors, the cylinder heads are re-cast replicas of the original units. The cast-iron heads are void of water passageways, outfitted with massive 2.0-inch diameter intake valves, Jesel roller rockers and lifters, 7/16-inch chromoly pushrods from Smith Brothers, and fasten to the block by way of 9/16-inch ARP studs. On the intake side, they flow nearly double what the factory 7.3L heads do.

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Surrounded by the one-off D&J Precision Machine billet-aluminum intake manifold, you’ll find an inline eight-cylinder P-pump from Northeast Diesel Service. The Bosch P7100 was treated to 13mm plungers and barrels, is capable of flowing 950cc of fuel (although it’s typically set at 550cc), and is locked in at 35 degrees of timing. The P-pump is also self-contained, with its oil being changed every six to eight hooks. It feeds fuel to eight billet-body, dualfeed International-style injectors from Scheid Diesel.

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A Holset HX60-based turbocharger from Columbus Diesel Supply sits behind the passenger-side headlight, with its corresponding velocity stack conveniently tucked in just behind the grille. Per the rules of the Limited Pro Stock Diesel Truck Class—the category the Unlimited guys spend most of their time competing in—the smooth-bore, journal-bearing charger features a 76mm compressor wheel (3.0-inch) and is void of a map groove. Mid-stride, the Columbus charger produces 50 psi of boost and roughly 65 psi of drive pressure, yet spins 130,000 rpm.

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To keep high intake air temps at bay, a Precision Turbo & Engine PT4000 water-to-air intercooler was sourced from Elite Diesel Engineering. The combination of the PT4000, a 240gpm belt-driven water pump from Haisley Machine, and more than 100 pounds of ice being utilized inside the truck’s insulated weight box drops boosted air from 600 degrees to roughly 50 degrees when hooked to the sled. The efficient water-to-air intercooler arrangement also limits peak EGT to a safe 1,600 degrees.

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Ensuring no vital area ever goes without oil, a dry sump oiling system is employed. Obtained through TFS Performance, the raceready oil system entails an R&R Racing Products pump, Peterson tanks, and a customfabricated Moroso oil pan. The dry sump system features four scavenge stages and two pressure stages, circulating 130psi worth of oil pressure throughout the engine. To guard against catastrophic failure, the engine, turbo, and injection pump all benefit from their own dedicated oil systems.

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Concealed within a blowproof aluminum Browell bell housing is a four-disc Crower clutch spec’d from Rursch Specialties. Behind that you’ll find a familiar transmission: the one-speed reverser. The Pro Fab Machine unit is graced with a 1.5-inch input shaft.

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Also from Pro Fab Machine, a quick-change transfer case sends engine power to both axles. For utmost strength, 1550 Series Dana Spicer U-joints are employed throughout the driveline. For utmost safety and containment, drive shaft loops are also in place.

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With a Rockwell 20-145 bolted under the truck, the rear axle will likely never give them any problems. The massive axle has been treated to a fabricated-aluminum differential housing, SCS Gearbox’s 2-1/16-inch, 32-spline axle shafts, and a spool. Up front, the Ford Dana 60 benefits from a set of Dana 70 axles and a spool.

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The tried-and-true BFGoodrich All-Terrain T/As, measuring 315/75R16, are relied upon to dig the old Ford through the dirt as quickly as possible. The DOT tires mount to 16×12-inch Real Racing wheels, which bolt to SCS dual rear wheel aluminum replacement hubs.

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Thanks to a TS Performance Informant data acquisition system, Bailor and Burnworth are able to log EGT in all eight cylinders, intake air temperature (before and after the intercooler), turbo shaft speed, oil pressure, fuel pressure, rpm, ground speed and many other vitals. The recorded information is used to diagnose a problem, deduce whether any changes made helped or hurt them, or both.

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Dale and Jamie Young, formerly of Extreme Collision Repair, were responsible for resurrecting the truck’s original body lines, fabricating the cowl hood, and applying the old-school, two-tone paint scheme. As for the project as a whole, Bailor and Burnworth are forever indebted to family and friends and especially their beautiful wives, who allowed them to pursue their P-pumped 7.3L dream. Most importantly, they live by Philippians 4:13, which states, “I can do all things through God who gives me strength.”

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Even though Bailor and Burnworth acknowledge their P-pump 7.3L creation is a little shy on horsepower compared to other trucks in their class, it didn’t stop them from finishing Third Place in the competitive Central Ohio Truck Pull Circuit in 2017. And while they plan to continue running the 3.0 smooth bore class in the future, they aren’t against competing in unlimited turbo classes from time to time. After all, a quick 300 to 400 hp can be added by turning up the P-pump, bolting on a larger turbo, and running the engine upstairs.

SPECIFICATION

1981 FORD F-350

OWNERS: Ben Burnworth, Nate Bailor
HOMETOWN: Bremen, Ohio & Lancaster, Ohio
ENGINE: 7.3L Power Stroke SHORT BLOCK: Concrete filled, fire-ringed cast-iron block with Hypermax bed plate, ARP 9/16-inch main studs, R&R Racing Products forged-steel rods, D&J Precision Machine FSR fly-cut pistons, custom profile camshaft (courtesy of Bob Holmes)
HEADS: D&J Precision Machine solid replica (re-cast) heads with larger intake valves, ARP 9/16-inch head studs and cut for fire rings, Jesel roller rocker arms and lifters, Smith Brothers 7/16-inch chromoly steel pushrods
OIL: R&R Racing Products dry sump oil system with Moroso custom oil pan, R&R pump, Peterson tanks
FUEL: Northeast Diesel inline-eight cylinder 13mm Bosch P7100, Scheid-built, International-based billet body dual-feed injectors with 5×18 nozzles, Waterman mechanical lift pump
AIR: Columbus Diesel Supply 3.0-inch smooth bore turbo, Precision Turbo & Engine PT4000 water-to-air intercooler, D&J Precision Machine billet-aluminum individual runner intake manifold, AutoMotion Design and Fabrication 2-inch-diameter stainless steel headers
ELECTRONICS: TS Performance Informant Pro data acquisition system
TRANSMISSION: Pro Fab Machine one-speed Reverser and quick-change transfer case with 4-disc Crower clutch and Browell blow-proof bell housing
HORSEPOWER: 1,100 hp (engine dyno)
TORQUE: 1,800 lb-ft (engine dyno)
TIRES: 315/75R16 BFGoodrich All-Terrain T/A
WHEELS: 16×12-inch Real Racing Wheels
AXLES: Rockwell 20-145 with fabricated aluminum differential housing, SCS 2-1/16-inch 32-spline axle shafts, spool (rear), Dana 60 with Dana 70 axle shafts and spool (front), 1550 series U-joints throughout
CHASSIS: Draw bar, front and rear end, hitch and driveline work performed by Jason O’Brien at Performance Truck & Tractor