Today’s competitive diesel scene, whether you sled pull, drag race, compete in dyno challenges – or all three – is chalk full of impressive, over-the-top engine builds that push the limits of aftermarket performance parts. However, as more and more shops focus on complete engine builds, fewer shops are focused on pushing the absolute limits of a stock diesel engine, especially without ever taking off the cylinder heads.
That’s exactly what Walt Schiemann, owner of Prime Diesel & Automotive, has been doing with the shop’s drag truck – a 2005 regular cab long box with a stock LLY Duramax under the hood. While the team at Prime Diesel & Automotive is utilizing a stock engine, they’ve been using enough fuel and air to run well under 7-seconds in the 1/8th mile. It’s no slouch!
We caught up with Walt on his 51st birthday back on July 22 to hear about how the Petoskey, MI-based shop got to where it is today and how this stock Duramax project came about.
“I’ve been around this stuff for a minute,” Schiemann says. “I grew up on a farm and always like tractors and whatnot. When I was in high school, I worked at a trucking company just doing basic repairs. When I got out of high school, I went to college for heavy equipment diesel. My focus when I was going to college was loaders and excavators and all that kind of stuff. I worked at a diesel shop on big semi trucks while I went to school to put myself through school. When I got out, I got a job in Petoskey at a GMC dealer.”
Knowing that Walt had a background working on diesels and enjoyed that kind of work, the dealership let Walt work on the 6.2Ls and 6.5Ls from back in the day. When the Duramax platform came out, that became Walt’s focus.
“The Duramax was a lot of fun because it was intercooled and direct injected,” he says. “I soon bought my own Duramax and my passion went crazy from there. I had an LB7 that ran pretty good and then I had an LLY and then an LBZ. I bought a brand-new LBZ in 2007 and I still own it and I’ll never sell it.”
Schiemann spent 25 years working for the dealership before he decided it was time to move on and do something else. He started Prime Diesel & Automotive just five years ago in 2016. The shop focuses on Duramax, of course, but also Cummins and Powerstroke work, and is currently expanding its shop space with a brand-new building.
“Our primary focus is the big three – Fords, GMs and Dodges – we do a lot of work on those,” Schiemann says. “We favor the GM and the Cummins platforms a little bit more than the Fords, but we don’t exclude the guys with the Fords. We do a lot of maintenance and repair. We’ve done a lot of Work Stock truck pulling engines, but we’ve also started getting into some drag racing.”
For machine work, Prime Diesel relies on other local machine shops due to the small size of the current shop. The new building Prime Diesel is completing, which is in the same location, will be much bigger.
“My current shop is two different buildings,” he says. “Our main shop right now is 1,450 sq.-ft. and the addition is 784 sq.-ft. We’re at about 2,200 sq.-ft. and we’re jumping to 6,500 sq.-ft. The new space has real tall, 24-foot-high ceilings. I’ve got some monster portable hoists that I can use if I want to do a big box truck and lift it up in here, I can. I can lift up a semi in there if I want to. At 6,500 sq.-ft. it’s the biggest possible building I could put on my current site and still be able to use it. It’s got eight bay doors.”
While the new shop space has been a priority lately, so too has the shop’s 2005 LLY Duramax drag truck. Ultimately, Walt and his team want to push it until something fails, but they’re fairly confident they can reach 1,000 horsepower and want to see the truck run under 6-seconds in the 1/8th mile.
“Our drag truck is a stock motor that we’re pushing the limits of,” Schiemann says. “We’ve never taken the heads off of it and we’re trying to see how far we can push it. It still has the factory head bolts in it and still has the factory balancer on it. We didn’t touch the engine for a reason – to see if we could make this thing run. Obviously, it doesn’t fit the normal Engine Builder magazine profile, but it’s something you don’t see every day. We have a lot of good fuel and air and it’s doing pretty good.”
The project ultimately started because Prime Diesel wanted to do a build without pumping a ton of money into it. The 2005 LLY Duramax truck had been sitting for a while and even had a tree fall on it, but Walt figured it was the perfect fit for this experimental project.
“We didn’t want to dump a bunch of money into this project because we wanted to see if we liked it,” he says. “We pulled the engine, transmission and transfer case out of it and decided to see what we could do with it.”
Walt got some additional help from Tony Burkhardt of Dirt Hooker Diesel, Eric Merchant of Merchant Automotive, as well as Danville Performance and Exergy, among others.
“We put a ton of air and a bunch of fuel to it – 300s and a 12mm – right away,” Schiemann says. “I got a turbo from Mark at Danville Performance. He’d gone through the turbo on it and I plumbed it in. We took the trans out and went through that a little bit with help from Tony’s son, Tyler. We got all the parts from Xcalliber on the trans and ended up putting a billet output shaft on it.
“Danville supported us, Xcalliber supported us and Tony/Dirty Hooker Diesel supported us. Eric supported us with some motor mounts. Exergy has been a big supporter of the project. Being a dealer for them, they obviously gave us a good deal on everything.
“I ended up buying a rolling chassis for it from a guy down south. The chassis was actually a pretty good competitor at some point. It’s been a fun little project to just kind of throw together, go out and see what we can do.”
Helping push the limits on this LLY Duramax is a five blade 72/83mm turbo as well as a 12mm fuel pump from Exergy and a FASS 290 lift pump. Prime Diesel is also using 300% over LLY injectors.
“I have a 14mm pump on the shelf that I’m going to put on it for the next trip out because we’re running out of fuel,” Schiemann says. “I can’t keep up with the fuel demands, believe it or not. We’ve also been throwing some nitrous to it, so it runs pretty clean.
“Right now, we’re only using a 50-shot of nitrous. We’re only in tune three on a DSP5 switch because we’re running the rail down on fuel because we’re putting so much fuel to it. There’s no smoke when its running down the track, so we know we’re getting everything out of it in tune three right now. We’re thinking once we get the 14mm on there we can actually keep up with demand and we can turn it up.”
In its current form, the LLY is running somewhere between 6.6-6.7 seconds at 103 mph in the 1/8th. Walt runs the truck at Onaway Speedway.
“We got a fastest time in the 500 feet up at Onaway Speedway going uphill and that’s a rush like no other when you break the edge of that hill and you cross over that,” he says. “They were saying we were breaking 100 mph at the top and that was only 500 feet. Going 100 mph in the 1/8th mile is cranking right along.”
While Walt is already impressed by the stock engine’s performance, he knows there’s plenty more left in the tank before the Duramax might give way.
“I have some fiberglass doors I want to throw on it,” he says. “Tony’s welder is actually fabbing up some brackets for me for a fiberglass bumper too. We’re going to put that stuff on to save some weight. We’re going to shave as much weight as we can. We’re somewhere around 5,000-5,500 lbs. right now.
“The doors and the bumper will help, and I think there’s some other things we can lighten up on a little bit just to try to save the motor a little bit. We don’t want to purposely go out and break it. We want to bring it up slowly. We don’t want to kill it all at once.
“We’re guesstimating, based on everything we’ve seen, that the engine makes somewhere between 800-900 horsepower. I don’t want to put it on the dyno and kill it. I want to keep it on the track and keep it alive as long as possible. My goal is to be able to put it all the way to tune five and actually get it to come out of the hole and get it to go down the track and see what numbers we can get out of it.
“If I can get under a 6-second pass with a stock engine, that’d be awesome. I don’t know if that’s attainable or not. At some point, I’m sure the rods are going to hate life and decide to come out. At that point, it’ll get a build.”
For now, things are looking promising, and once the 14mm fuel pump is installed and more nitrous can be used on a higher tune, Walt says the 1,000-horsepower mark could be possible.
“We can put the 14mm on and then bump it up another notch and start bringing on some more nitrous,” he says. “Right now, the turbo is not limiting us because we can add some more nitrous to it, so we’re just planning on leaving that for now. I think if I put compounds on it, we’re just going to destroy the motor.
“It’d be really cool if we can get close to that 1,000-horse mark out of a stock motor. More than anything, I want to just see how far we can go. We are only guesstimating on that 1,000-horse mark. Can we make it? We don’t know. There’s other guys out there doing this. We’re not the only ones. There’s probably other guys out there who already have some records. I don’t care if we beat anybody’s record. This is just something we’re having fun with. In drag racing, it’s all about how fast you can get down the track.”
Time will certainly tell how far this LLY Duramax will go, and at that point, Walt says he’ll decide whether or not to build up an engine for the truck or put another stock engine in it. One thing Walt knows for sure is the shop has demonstrated that an engine setup like this one could benefit a guy on a budget who doesn’t want to get into a full, custom engine build, but still wants good horsepower and speed.
“Pushing the limits of what a stock engine can actually do has been pretty cool,” he says.