The Hummin' Cummins

The crazy Cummins-powered H1 Hummer

April 2021 Feature Clyde Turner

This article originally appeared in the Winter 2020 issue.

Here’s something you definitely don’t see every day! It’s an H1 Hummer with a Cummins turbo diesel. And making it even more interesting, it’s a 12-valve engine! Steve Ortner, the owner of Mountain Machine in Belleville, Mich., the shop that completed this build, has owned this Hummer for four years, and there’s no doubt this thing is a beast!


“I always wanted an H1 Hummer, so I bought one and I was going to put a Duramax in it, but then I rode in a friend’s truck, which was a crazy day cab Peterbilt with an N14 Cummins, so that really got me hooked on the Cummins idea, just the way that truck sounded,” Steve says. “Then one day I was watching [Vegas Rat Rods] and I decided I wanted to do compound turbos on this Cummins and then it just snowballed from there, turning into the idea of the ultimate angry diesel-powered American truck.”

Steve’s Hummer is definitely at the top of the line when it comes to extravagant vehicles that are custom to the core.

“It’s actually a 6.7L motor with a 12-valve head on it, and it’s been machined with a ton of our billet components and other stuff we make,” Steve says. “That’s because the old 12-valve 5.9L blew, so we salvaged it and morphed it with the other stuff.”

The modified engine well represents the main idea of the custom fabrication Steve’s shop is all about. He has showcased his Hummer at a few shows, a notable one being the Scheid Diesel Extravaganza back in August. The truck spends time at shows regularly, but it spends much more of its life as Steve’s weekend warrior and “fun” vehicle.

The Build

As you might imagine, this Hummer has a laundry list of upgrades done to it under the hood that’ll blow you away. Of course, the biggest one is the Hamilton 6.7L engine wet race engine block with the stock 5.9L Cummins crank and fully ported and shaved large-valve Cummins head, but the other mods say a lot as well. They include Wagler billet rods, Diamond billet steel short projection height pistons, a Hamilton 188/220 camshaft, a custom billet runner intake fabricated in-house, an in-house custom billet gear case, a Farrell Diesel 14-millimeter P-pump, a Waterman lift pump, a Steed Speed exhaust manifold, Scheid Diesel 5-by-1/4-inch dual feed injectors and .120-inch fuel lines, and a Fluidampr Competition Series balancer.

“Apex Turbo supplied the 110/114-millimeter GT55 turbo with a billet center section and backing plate, S400 86/88-millimeter turbos as well as the water methanol system,” Steve says. “All the plumbing was supplied by Vibrant performance and the radiator is a Ron Davis performance radiator.”

With all of these components set up, Steve already has an impressive racing machine, but that’s not all. To support all this crazy power, the Hummer needed a built up transmission as well, so Steve fit in a 4L80E transmission and added a plethora of internal upgrades there. Putting the power on the ground are Raceline wheels, along with tires from Duneland Off-Road Center in Mears, Mich., cut by Scott Carlson.

“That guy’s the master,” Steve says. “He sure helped throw together a great truck.” Finally, the paint job was completed by Casey Curtis, a good friend of the Mountain Machine shop.

Usage & Future Plans

Steve spends a lot of time racing the Cummins-powered beast out on the dunes. “I’ve always been a sand dune guy; I have a cottage up at Silver Lake Sand Dunes up in northwestern Michigan, and I really enjoy it up there,” he says. “The Hummer is mostly a sand dune vehicle but it’s decent enough to drive on the street when you need something to get around.” Steve has also taken his rig to plenty of shows aside from the Scheid Diesel Extravaganza, including the Moab 4x4 Expo in Utah.

“It was going to be at PRI and SEMA this year, but that’s obviously not happening due to COVID,” he says. “But hopefully we’ll be able to make a full round next year.” With Steve’s project complete, he says it now feels totally different, during both night and day, from what it used to be.

“I’m thinking it’s now close to 1,500 horsepower with the boost at 70 psi,” he says. “It’s like nothing I’ve ever driven before; in the way it pulls, it’s just a totally different animal.”

Steve had put so much into the build, and he says there’s no way he could have done it all himself. “I owe a special thanks to Ed Larsen, Carl Sparks, Casey Jewell and Doug Strimpel for all their hard work and dedication,” he says. In the future, he plans on hitting up plenty more sand dunes across the country, including in states like Oklahoma and Idaho.


Apex Turbo

Diamond Pistons

DuneLand Off-Road Center

Farrell Diesel Service


Hamilton Cams

Mountain Machine

Raceline Wheels

Ron Davis Racing Products

Scheid Diesel

Steed Speed

Vibrant Performance

Wagler Competition

Waterman Racing Components

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