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.”
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.
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.
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
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