When it comes to high performance diesel, Eddyville, Iowa’s AJ Hynick didn’t start in the kiddie pool; he jumped in the deep end with both feet. AJ is the driving force behind Hynick Performance Diesel (HPD), and the mastermind behind his brother’s 600hp Duramax you’ll find elsewhere in this issue. When it came to his own truck, he got a little carried away, first on the sled pulling circuit and then in some serious drag racing.

When he first acquired his ’03 GMC 2500HD, Hynick had the sledpulling bug bigtime, and set out to dominate the local pulling scene. With a four-year string of points championships from 2009-2012, he eventually started to look elsewhere for his performance kicks. So when it came time for a revamp of the truck, he decided to tackle the dragstrip, while keeping the GMC suitable for use on the street.

2003 LLY…

The basis of the 6.6L Duramax engine is actually an LLY rather than an LB7, but virtually none of it remains stock. Early on, AJ got hooked up with TTS Power Systems out of Compton, California, and you’ll find TTS’s go-fast parts all over the engine. The short block has a factory crank, but virtually everything else has been upgraded. TTS supplied the rods and pistons, as well as a custom race camshaft. ARP main studs were used, but the head studs are from TTS. Finally, the short block was topped with TTS race-ported heads with TTS valve springs.

The stout, square water-to-air intercooler up front looks more like a fuel cell than a heat exchanger, but its massively thick core makes for a huge drop in turbocharger discharge temperatures.
Hynick built the side-mount turbo kit himself; it is responsible for the unique snarl that the Duramax engine gives out when it’s lit up. A crossover tube brings exhaust gases from the driver’s side and meets up with the passenger side in a T6 flange to mount the turbocharger.
With an estimated 1,100 rear-wheel horsepower, the 6.6L Duramax in AJ Hynick’s ’03 GMC just plain outpaces most of his competition. The fact that he’s able to make that kind of power on a single turbo, without nitrous oxide, is even more impressive.


With his sled pulling background, Hynick stuck with a single turbo when it came to the drag racing swap. He started out with a Topkick manifold and a BD manifold, both facing forward. From there, he relocated the turbocharger from the valley of the engine to the side, using schedule 40 piping and a T6 flange. The Holset HX60-based charger features a billet Columbus Diesel compressor wheel that has a 3-inch inducer and cranks out an impressive 65 psi of boost. The intercooler side also got the treatment with a large air-to-water intercooler from Frozenboost.

The Holset HX60-based turbo is about as serious as they come. With a compressor wheel from Columbus Diesel, the turbo makes 65 psi of boost and only 76 psi of drive pressure. Exhaust exits through a 5-inch downpipe.
Worrying about exhaust restrictions isn’t a problem, as Hynick runs a 5-inch exhaust back into a chrome 6-inch stack that’s mounted in the bed.



It takes a pretty serious amount of fuel to break the 1,000hp barrier, so Hynick designed most of his fuel system for overkill, just in case. From the chrome IMCO tank, fuel flows into twin FASS pumps; the first is a 240gph unit, and then to maintain pressure there’s a second 150gph pump that’s triggered at 20 psi of boost. The engine’s factory LLY CP3 pump is still there, but it is supplemented by a second CP3 that’s mounted with an ATS Diesel kit. Finally, Hynick again turned to Steve Cole for a custom set of TTS injectors. Tuning was handled by AJ himself through EFILive software.

In case of an accidental runaway situation, Hynick runs a flapper-style air guillotine so that the engine can be shut off with just the pull of a cable.
A huge icewater tank for the intercooler is mounted right behind the driver’s seat and circulates water through the intercooler. The tank was made by Dad’s Intercoolers and holds 80-100 pounds of ice.
A single CP3 could only provide about half the fuel that Hynick was looking for, so a second pump was mounted using an ATS kit. The twin pumps send fuel to a set of custom injectors from TTS Power Systems.
The bare-bones interior is typical of a street/strip truck. Hynick didn’t completely gut the cabin, since he still wanted to enjoy driving it, but the fire extinguisher, multitude of gauges, and kill switches point to a rig that sees plenty of track use.


Allison 1000 transmissions are pretty strong in stock form, b ut Hynick knew his would need major upgrades to withstand four-digit power. This meant installing TTS input and output shafts, along with an upgraded C2 hub. A Suncoast Diesel P2 planetary was also installed, along with an experimental torque converter from Goerend Transmissions to help spool the big turbo. Hynick built the transmission himself and even performed some TCM tuning and installed an ATS Co-Pilot to firm up the shifting.


With a big-horsepower engine and stout transmission, the final step was making sure the power got to the ground. Here, too, Hynick wasn’t going to skimp out, as the truck needed to be reliable when storming down the track. Much of the rear axle is left over from his sled pulling days, which means it’s pretty stout. After a set of 3.42 gears were installed, an All Season Service and Sales spool was added, along with a set of 38 spline axles. A 4-inch driveshaft was fabricated and connected to the rear end via 1480 U-joints. The front axle has also been upgraded with 3.42 gears and a complete Exaxt front suspension kit.

Twin FASS fuel pumps are mounted on the frame and feed the hungry Duramax engine. A 240gph pump is on all the time, while a second 150gph pump is activated at 20 psi of boost.
Virtually all of the intake piping was built through AJ Hynick’s shop HPD, and features 4-inch intercooler in, out, and custom intake-to-engine piping.
A set of 305/50R20 Nitto 420S tires provide grip no matter the usage. The wheels are 20×10-inch BMF Novakanes.
The rear suspension still has its sled pulling-style traction bars attached, and they work quite well for drag racing too. So far, Hynick has cut a best 60-foot time of 1.65 seconds, although he thinks he can shave a bit more off in the future.


After years of building and executing his idea of the perfect Duramax-powered street truck, it was time to put down a number at the track. With the GM still sporting Nitto 420S street tires, AJ Hynick’s first trip to the local eighth-mile resulted in him cracking into the 6s with a 6.97-second elapsed time. The truck has since run a best of 6.93 at 104 mph, sealing its status as a mid 10-second street ride, and putting a big smile on the owner’s face every time he gets behind the wheel. DW

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