Justin Hieserich’s Durmax Powered 1994 H1

The HMMWV (later nicknamed Humvee) was introduced in 1985 as a military vehicle that proved to be an extremely versatile platform. Since then, it has been an active military vehicle for more than 70 nations. The HMMWV was created and manufactured by AM General. In 1992, AM General began manufacturing a civilian version of the Humvee called an H1 under the brand name Hummer.

A couple of years later, Justen Hieserich’s 1994 Hummer was manufactured. While the original configuration was considered plush by military standards, in the consumer world, these vehicle were far from it. A doctor in Texas bought the H1 new and after a few years sold it to another gentleman, also, in Texas. Thanks to a divorce, he had to sell the H1 and that is when Hieserich’s father picked up the H1 and moved it to Minnesota.

In 2002, Hieserich’s father bought the H1 at a police auction. While it served as a fun, “look at me vehicle,” it ended up sitting a lot. The neck breaking 155 horsepower and 275 lb-ft of torque producing 6.5-liter just wasn’t that fun to drive. In fact, after only a couple of years, Hieserich ended up burning up all 8 pistons pulling his bull dozer around.

Justin, who owns Pick Ups N’ Power Sports, decided it was time to do something with the H1. At the heart of the H1 is the Detroit Diesel and as far as Hieserich was concerned, it was also the heart of the problem. So he picked up an ’03 LB7 Duramax engine to serve as a donor for the transplant.

Hieserich started out by stripping the engine all the way down to a bare-block and upgraded the key parts that were going to fail if he decided to push the engine down the road. The upgrades started with fly cut Mahle Motorsports pistons and Carrillo rods. He left the crank alone, but did opt to install a custom Comp Cams camshaft as well as upgrad the head bolts to ARP studs.

Once the long block was assembled, Hieserich focused on air. He opted to run a Garrett 4202 turbocharger. The 74-mm turbocharger doesn’t spool up anywhere near the factory charger. To ensure that the truck could still be driven, Hieserich installed a BD Diesel Performance diverter valve.

The diverter valve usually mounts on top of the turbo pedestal causing the charger to stick up a little more than usual. Hieserich didn’t want the charger to stick up that much, so he had the pedestal machined and now the diverter and pedestal are the height of just a standard pedestal. Not only does he like the way this looks, it has a side effect of adding more clearance between the firewall and the engine.

Now with a charger that could support close to 1,000 horsepower, Hieserich knew he could go pretty large with the fuel. He turned to the guys at Industrial Injection for their dual CP3 kit. He then upgraded his injectors to Exergy Performance 100% overs. While these aren’t crazy big, they can support enough horsepower to make the H1 a really fun ride without hazing too much. To ensure the CP3s have enough fuel, he custom fabricated a second fuel tank and connected both to a Fuelab lift pump.

Behind the engine, Hieserich opted to install an ATS billet flywheel. An Allison 6-speed transmission was completely overhauled and built by Hieserich using a SunCoast transmission kit. Even with the diverter valve, Hieserich opted to install a 3,000 rpm stall converter just to give him the best driveability he could get.

Once the powertrain was assembled and ready, he dropped it in between the frame rails. Once it was situated where he wanted it, he went to work mounting the ancillary components. He started with custom fabricating the exhaust system connecting to a set of 6-inch MBRP stacks. Then, he added a Snow Performance water-methanol injection kit and a custom Griffin radiator.

Because of how the radiator mounts in the H1, Hieserich couldn’t use an engine mounted fan. After spending quite a bit of time looking around, he eventually settled on a dual fan setup off of a Ford Taurus. The final piece of the puzzle was the intercooler. Hieserich turned to Griffin again and had a custom intercooler fabricated to work with everything.

Once the powertrain was ready to make power (thanks to the EFILive tuning), he turned his attention to getting the H1 moving. Hieserich decided that the AM General axles were fine, but he upgraded the rear yoke and CV joins to later ’06 units. The ‘06 line was larger and designed for the increased horsepower and torque of a stock Duramax.

For rolling stock, a set of 38×15.5R20 Mickey Thompson Baja MTZs encompass 20-inch KMC Rock Star wheels. Now these are pretty tall tires at 38-inches and to clear them, Hieserich ended up installing a 9-inch suspension lift and a 3-inch body lift.

With the truck sitting proud, he needed an easy way to get into the truck, so a set of AMP power running boards that were designed for a Jeep TJ were installed.

For the finishing touches on the exterior, Hieserich did a Xenon HID headlight conversion, installed a B&W Turnover Ball gooseneck hitch and a soft tonneau cover.

In the interior, he upgraded and added Auto Meter gauges to keep an eye on the key vehicle information. Then he installed an Edge Insite to monitor the engine and transmission vitals.

The seats, door panels, and headrests were all redone and sport the yellow and black theme along with H1 and Hummer stitching. Hieserich isn’t done and still has a lot of plans for the H1, but is happy where it is.

The best part is he has lost none of the Hummer traits. In fact, Hieserich reports that he has kept all of the factory fording stuff and even if the truck hadn’t been lifted would still be able to forge through 36-inches of water. With the lift, he should be close to 48-inches now.