It’s battle-hardened vs. brand-new, VGT vs. fixed geometry, and Allison vs. ZF-6 in this husband-wife pulling partnership.
Dan and Heather Clarke are partners in life and in business—but catch this husband-and-wife duo in the dirt and you’ll find them to be fierce competitors. Both share a passion for the Duramax platform and for truck pulling, and each of them pilot their own Chevrolet Silverado in the Work Stock diesel class. Heather and her ’02, an extended cab short bed named “Hank,” have a history of success behind them, having racked up over a decade of seat time and more than half a dozen points championships. Dan campaigns an ’05 crew cab that’s relatively new to the scene but that came on strong at the end of the 2025 season.
They also happen to own and operate Dan’s Diesel Performance, a company that builds its own line of turbochargers and, in recent years, its own common-rail fuel injectors and CP3’s. As you might’ve already guessed, truck pulling is a great way to test the capabilities of cutting-edge turbo and injection components—and that’s exactly what Dan and Heather do with Hank and the ’05. “What started off as a hobby has grown into a passion,” Dan told us. “We are pushing the products our customers would be purchasing. We are running the same turbos, pumps and injectors we sell, so everything is tested and proven.”
How proven? For starters, both trucks were knocking on the door of 1,000 hp the last time they hit the chassis dyno. Keep reading to find out how the Clarke’s put that kind of power to use in the dirt.
The ’05
If your engine is going to live at four-digit horsepower, you better make it as bulletproof as possible—and Dan relied on some of the best in the business to make that happen for his ‘05. A Dan’s Diesel Performance (DDP) “budget built” short-block utilizes a Callies crank within an LLY block. It’s anchored in place via billet main caps and main studs. The rest of the rotating assembly consists of a set of DDP Dominator connecting rods and 16.5:1 compression Mahle Performance Cast pistons. A SoCal Diesel alternative firing order camshaft (6480) actuates the valvetrain while a pair of ported, big-valve LBZ heads from Wagler Competition Products—and that started out as brand-new castings from Fleece Performance Engineering—allow the Duramax to breathe. The high-flow heads fasten to the block by way of DDP head studs and are topped off with a Wagler street performance intake.Perhaps no other form of motorsport has accelerated turbo innovation the way truck and tractor pulling has. Here, most classes dictate strict turbo size limitations, so it’s up to turbo makers to find a way to squeeze as much usable power as possible out of their products. This is how Dan does it on the ‘05. With his local Work Stock rulebook permitting the use of any size drop-in, stock-appearing turbo, or up to a 69mm BorgWarner S300 (S369), he opted to push the limits of a Garrett GT3788VA based VGT. Coined the Competition Dominator, it sports a 72mm compressor and a 9-blade, 74mm/80mm turbine wheel, both of Dan’s own design. Heavy-duty shaft bearings and a 360-degree thrust bearing assembly help it survive the 40 to 45-psi of boost it sees. The Competition Dominator charger’s remote mount location (which also fits his local sanctioning bodies’ rules) makes the R&D process much easier, with turbo swaps being performed in minutes as opposed to hours.A 165-gph FASS system mounted along the driver side frame rail supplies ample fuel pressure to one of Dan’s 14mm CP3’s. The stroker pump, which resides in the factory location, has proven capable of supporting 1,100-rwhp in LLY Duramax applications (and 1,300-rwhp in L5P trucks). The competition-friendly CP3 sends high-pressure fuel through the rails and ultimately out to a set of Dan’s injectors. The worked over units feature internal body modifications and are capped off with 300-percent over nozzles. Thanks to the lightning quick injection rate the injectors provide, just 1,300 microseconds worth of duration (injector on-time) were needed for the ’05 to clear 945 hp on the rollers.With the brunt of the sled bearing down on the rear axle, Dan made sure it was fortified enough to handle the abuse. The AAM 1150’s differential was fitted with a G80 mini spool from Dirty Hooker Diesel (DHD), Yukon Gear & Axle chromoly 30-spline axleshafts, and a 4.56:1 ring and pinion (front and rear), which helped Dan achieve the exact final drive ratio he was after. Rear axle wrap is non-existent thanks to a set of traction bars Dan built himself. They boast sizable 2.25-inch diameter DOM tubing and 1.25-inch diameter heim joints. Up front, the factory AAM 925 IFS is reinforced thanks to a Kryptonite ultimate front-end package, an Eaton ELocker, and also benefits from DHD front (and rear) suspension stops.A Dan’s Diesel Performance Dominator Allison Comp 2 is tasked with harnessing everything the Duramax dishes out. The five-speed automatic benefits from billet input, intermediate, and output shafts, a billet C2 drum and P2 planet, Alto G3 C1 and C2 clutches, Alto G3 C3 and C4 clutches with Kolene steels, and a mix of TransGo and RatioTek upgrades in the valve body. Behind a billet flex plate, a Goerend BX torque converter sits on the input shaft—a billet front cover unit with a billet stator and a 2,600-rpm stall speed.With the Allison locked in fourth gear (and the transfer case in Low range), Dan locks the converter via his DHD lockup switch almost as soon as the sled gets moving. From there, the ’05 picks up ground speed quickly, the Duramax carrying 4,000 to 4,200 rpm heading down track. Depending on track conditions, Dan either runs a set of 35×12.50 Venom Power Terra Hunter X/T’s or the 35×12.50R17LT Kenda Klever M/T’s you see here. Dan and the ’05 would earn three wins and several Second Place finishes in 2025, including a 366-foot victory at the Hub City Dirt Drags. We’ll give you one guess as to who he finished a few feet short of during most of those runner-up performances…
“Hank”
The fortifications run deep in Heather’s battle-hardened Silverado (“Hank”), and it all begins with a DHD short block. Starting with an LML Duramax block (chosen for its stronger casting), it was bored, sleeved, and machined to accept O-rings. It’s graced with a stroker crank from Winberg (overall displacement checks in at 7.2L), a girdle, billet main caps, and main studs. The connecting rods are billet-aluminum units sourced from R&R, their small ends accepting Hemi wrist pins and accommodating 16:1 compression Diamond pistons. A stage 2 alternate firing order camshaft from Callies operates the valvetrain, while a set of Wagler‘s ported LB7 heads—fitted with larger intake and exhaust valves—usher as much airflow as possible into the big cube Duramax.Like the ’05, you’ll find one of Dan’s remote-mount, Competition Dominator turbos under Hank’s hood. However, staying true to the LB7’s roots this IHI concept charger is a fixed geometry unit. Built from brand-new castings, it was machined to fit DDP’s desired turbine and compressor wheels, a 72mm compressor and a 10-blade, 74mm/80mm turbine, respectively. Heavy-duty journal bearings and a 360-degree thrust bearing assembly ensure the turbo enjoys maximum durability. The 72mm Dominator forces 40-psi of boost through a Spearco intercooler during the course of a pull.Thanks to a DDP 14mm CP3 in the valley and a belt-driven Sportsman pump up top, there is always plenty of rail pressure on tap for the monster-sized injectors Heather runs. Designed, built, and flowed in-house at Dan’s Machesney Park, Illinois location, the SAC style units are internally modified and equipped with 400-percent over nozzles. The competition injectors can deliver high fuel volume in a very short window, only requiring 1,250 microseconds worth of injector duration to make 991-rwhp the last time the truck was on the chassis dyno. The common-rail system is supported by a 240-gph FASS low-pressure system, complete with a Fuelab regulator.You won’t find an Allison behind the potent 7.2L Duramax that powers Hank. Instead, you’ll find the venerable ZF-6. The tough-as-nails six-speed manual has been along for the ride for countless hooks over the years and, incredibly, has never broken anything other than a tail housing. It’s fitted with a Valair triple-disc, sintered iron competition clutch with a weighted pressure plate and has a factory NV261 transfer-case attached to it—which has proven just as robust as the ZF-6. Locked in fifth gear (direct drive in a ZF-6) and 4-Low, Heather leaves the line at 4,500 rpm. Once she’s off the clutch pedal, rpm drops but quickly recovers and the truck typically carries 4,000 to 4,200 rpm down track, then spins out around 3,400 rpm.Thanks to a 2018 HD donor, the AAM 1150 was ditched in favor of this AAM 1180, chosen for its larger (11.8-inch) ring gear diameter, 4-inch diameter axle tubes, and bigger spindles. Like the AAM 1150 in the ’05, Hank’s AAM 1180 is fitted with a DHD G80 mini spool and chromoly 30-spline axleshafts from Yukon Gear & Axle. It’s also equipped with a 4.56:1 ring and pinion (as is the front differential) and is unable to rotate thanks to a beefy set of DDP traction bars. As for the AAM 925, it’s been treated to Kryptonite Death Grip tie rods, an Eaton ELocker, and Fleece TufShafts in the differential. A Tuff Country lift offers up 4-inches of added ride height up front, providing plenty of clearance for 35-inch tires.Heather and Hank have won seven (7) Work Stock points championships over the years, three with the Midwest Tractor & Truck Pullers Association and four with the Southwest Wisconsin Pullers (including this year). Within the latter organization, Hank proved dominant in 2025, winning four of nine pulls and ending up second twice. And when Heather and Hank couldn’t pull off a Top 2 finish, Dan and the ’05 usually could. It’s a back and forth they both enjoy. “We’re both naturally competitive,” Heather told us. “So it’s fun to pull against each other.” The husband vs. wife rivalry isn’t lost on the local pulling scene either, with announcers often hyping it up for the folks in the stands. “I usually pull first,” Dan tells us. “Then Heather will outpull me sometimes and the crowd loves it.”
