Dominating the Dirt: A Full-Pulling, Cummins-Powered Third-Gen Chevy
Now that we’re at the height of the truck pulling season, a few ring-leaders are beginning to emerge. Among the front-runners in the elite Lucas Oil Pro Pulling League’s Pro Stock Diesel Truck class, you’ll find Todd Cox’s ride: a 1980 bodied Chevy on a ’96 Dodge ¾-ton frame that’s powered by a 1,850hp Scheid-built 12-valve Cummins and driven by his 16-year-old son, Jayden. Coined “Boosted Outlaw,” Cox’s purpose-built puller has been darn-near dominant thus far in 2018. While it’s only accumulated one win, the truck has finished fifth place or better at six out of nine events. Trust us, consistency can be hard to come by in Pro Stock, where on any given night the class favorite can end up at the back of the pack and the underdog can steal the victory.
Along with current first place holder Matt Penn and third place competitor Rod Tarr, Cox is all but running away from the rest of the Pro Stock field in 2018—despite there being more than a dozen competitive trucks in the mix. How is he doing it? Maybe it’s luck, maybe it’s a combined 40 years’ worth of tractor pulling experience, maybe it’s the truck’s overall setup or maybe it’s a combination of all of the above. Either way, this truck is kicking ass and taking names—and as the season winds down, the Coxs are ramping things up for a shot at the Pro Stock title. Keep scrolling to find out how their 390 ci, inline-six squeezes 1,850hp through a single turbocharger, as well as how the truck survives its 15-second battles with the 40,000-pound sled.
Due to its increased block strength over the 5.9L crankcase, Cox’s Scheid-built Pro Stock engine is based on a 6.7L block. Further improving strength and reliability, the block’s water jackets are filled with concrete. It’s been machined to accept a girdle, 14mm ARP main studs (vs. the 12mm factory fasteners), cylinder sleeves and fire-rings, and incorporates a one-inch thick deckplate up top to keep the combustion area of each cylinder from distorting. A balanced rotating assembly consists of a stock 6.7L Cummins crankshaft, R&R Racing Products connecting rods and ultra-low compression (12:1) Arias pistons. A Wagler Competition Products 12-valve cylinder head—treated to heavy port work, oversized Inconel intake and exhaust valves, roller rockers, chromoly pushrods and a one-piece valve cover—anchors to the 6.7L-based block by way of 14mm ARP head studs. In order to clear the removable hood (and because Cox didn’t want to have to lift the truck’s body), the engine is cocked slightly toward the passenger side fender.
Capable of flowing more than 1,000cc of fuel, but typically set at the 800cc mark, is one of Scheid Diesel’s 14mm P-pumps. The high-flow P8600 houses 14mm plungers and barrels, a quick-rate cam and sports an RSV (“Ag”) governor. The big injection pump benefits from dual supply lines and a gear-driven Daryl Saucier Racing (DSR) lift pump feeding it 50 psi worth of fuel pressure. Pressurized diesel leaves the P-pump through large diameter (0.120-inch) stainless steel injection lines and a set of Scheid’s triple-feed injectors equipped with 5x0.030-inch injectors (five holes in each nozzle, with each measuring 0.030 inches) mix fuel with the compressed air in each cylinder.
At The Hart of the Build
Pro Stock class rules dictate that a single turbocharger must feed the engine and that the turbo has to be of a smooth bore design. This means no map width enhancement groove (also called a map ring or inducer bleed) can be present. All air must pass through the compressor wheel inducer, which can be no larger than 3.6 inches (roughly 92mm) in diameter. Despite these limitations, this turbo from Hart’s Diesel moves enough air to support 1,850hp. It builds between 50 and 55 psi of boost during the course of a pull.
With so much fuel on tap and the incoming air compressed to more than 50 psi, intake temperatures can crest 500 degrees F. To cool things back off before entering the head, boosted air is routed through this water-to-air intercooler. Highly efficient, the system drops incoming air temperatures from 500 degrees to as low as 70 degrees, meaning cooler, denser, horsepower-friendly air is all the engine ever sees. This one component is just as responsible for the Cummins’ 1,850hp output as its wild injection system or top-of-the-line turbocharger is.
As you can imagine, transferring as much of the engine’s 1,850hp (and more than 2,500 lb-ft of twist) to the wheels as possible calls for a heavy-duty driveline. Bearing the brunt of the abuse is the rear axle, a Meritor/Rockwell 20-145 in this case. Sourced from Proformance Pros, the 20-145—an axle with a 20,000-pound GAWR— sports a spool, a 6.20:1 ring and pinion ratio and gun-drilled axle shafts. Notice the rear axle is also void of any suspension system, which is purposely done to keep things as rigid as possible. For all intents and purposes, the rear axle is part of the frame.
Hybrid Front Axle
To keep the front wheels digging reliably, a custom military/Rockwell F106 axle from Proformance Pros is employed. The hybrid axle features military style outer knuckles and an F106 center section. In the differential, you’ll find a Detroit locker and a 6.20:1 ratio ring and pinion. Within the axle tubes, you’ll find 1.75-inch diameter axle shafts. Hydraulic steering allows the truck to be maneuvered around in the pits.
The 80/20 Split
Peering in through the driver side rear fender well you can see that no bed floor exists and that the back wall of the truck’s cab is gone. Ditching weight everywhere but forward of the front axle is the name of the game in the sport of truck pulling and Cox’s Chevy benefits from an incredible (for the Pro Stock class) 80/20 front/rear weight distribution.
Now this is what you call a gutted interior. After cutting out the floor of the cab, removing all windows and taking a hole saw to everything else, it’s easy to see the extent to which Cox went to scrap weight. In the photo above, you can also see the truck’s near-bulletproof drivetrain. From right to left: a Browell blow-proof bell housing concealing a four-disc Molinari racing clutch, fully-contained input shaft and one-speed Pro Fab Machine reverser transmission, which is bolted to a Pro Fab quick change drop box/transfer case (hence the second drive shaft routing power to the front axle).
10-Foot Bed & In-House Body Work
The longer the wheelbase the better in truck pulling, and by adding a 10-foot bed to the Chevy, Cox was also able to stretch the truck’s wheelbase to the 158-inch class maximum. Cox handled all auto body work as well, from the removable steel front quarter panels and hood to integrating illustrations drawn up by his niece into the truck’s paint scheme.
Worth the Weight
After all weight reduction measures had been completed, Cox was able to add weight right where it needed to be: forward of the front axle. In addition to housing the fuel and dry sump oil tanks, the ice box and the water-to-air intercooler arrangement, the weight box is chock full of tractor weights. In meeting the Pro Stock class’s maximum weight requirement of 7,800 pounds, the front half of the truck accounts for more than 6,000 pounds of Boosted Outlaw’s overall heft. As a result, the back of the truck can literally be lifted by hand.
Lead image provided courtesy of Amy Gilbert of Stainless Diesel