The Mighty 460hp Colorado

October 2020 Feature Colin Peterson

This article originally appeared in the September 2020 issue.

Here’s something you don’t see that often in our magazine; most of what we cover involves 3/4-ton and larger diesels as they’re the most capable trucks that are worth so much when you build them up. However, some folks don’t need a whole lot of truck and prefer the better fuel economy while still being able to haul a decent amount, and manufacturers have been catering to them since a few model years ago by including a diesel option in many of their half-ton and even mid-size models. This 2016 Chevy Colorado with the 2.8L four-cylinder Duramax is a Montana truck that was built by Jag’s Pro Truck Shop in Zimmerman, Minn., a shop we’ve covered a few other impressive builds with over the years. This truck is special not just because of its compact size, but it endured some torture to get it to where it is now.

“The finished product tested at 460.6hp on the dyno,” says shop owner Josh Gruis. “Not bad for a four-cylinder that put down 158hp stock.”

That’s actually quite impressive for an engine that small and the recognition it is now receiving is well-deserved considering all the trouble this truck went through to achieve it. The whole build proved to be a big learning process for the Minnesota-based shop.

Build Process

The owner bought his blue Duramax beast in 2016, which eventually found its way to Jag’s Pro Truck Shop.

“He had done other builds in the past, but since this was his first diesel he wanted it to be unique,” says Josh. “He reached out to our shop to find we were very eager to make a project out of his truck; he gave us the word and we went to town.”

The owner started with just some tuning, but it ended up not being enough for him, as he was back in the shop again after a few months to kick things up a notch with a new turbo kit, suspension, and tires.

“Those upgrades brought the horsepower up to 296,” Josh says. “However, the engine wasn’t handling the new turbo so nicely, and it blew its number four rod.”

At this time in 2017, as per the owner’s request, Josh’s shop had to ask GM to deliver them a new engine block; thankfully, the truck was still under warranty so one could be sent without the owner dumping thousands upon thousands of dollars. However, it took a lot of arm twisting.

“We had to kind of fight with GM for a new engine block as we kept getting asked, ‘Why do you need one? Why isn’t the truck at the dealer for warranty?’” Josh says. “However, we finally got a brand new block from GM and began to build it up.”

After a wait, Josh’s shop got their hands on one of the first sets of Carrillo rods; at that point, they built the pistons, keyed the cams and crankshaft, o-ringed the block and installed ARP head studs. The engine was then put back together with its same turbo kit add-ons. With all of these improvements, the engine was so much better designed for major upgrades, and it ran amazingly well.

Now that the turbo-ready upgrades on the engine itself were corrected, Jag’s discovered some intercooler issues.

“The factory one had plastic tanks and we blew the hot side right off,” says Josh. “At first to get us back in business, we bought another factory one and banded it so the tanks couldn’t move.”

For many applications, a turbo upgrade also requires an intercooler upgrade, and the folks at this shop learned that in a big way. To make a long story short, this new modified intercooler put up with the turbo upgrades so much better. The owner then went on his way to enjoy his power and undercarriage upgrades.

Getting There

However, after a year, the owner went back to Jag’s again. This time, the stock 6L50 transmission was wearing out from so much fun and it was time to fix it up as well. The Colorado owner didn’t just want to fix it; he wanted to give it a total makeover.

“He asked us, ‘How about a 400hp Colorado?’” recalls Josh. “I told him, ‘That’s a big pill to swallow with so little parts available and it seems no one is really playing with these,’ but of course I followed his requests and went through with it.”

After spending over a year at the shop with lots of thought and discussion with manufacturers and sleepless nights for the shop workers, the little truck finally surpassed the owner’s goal!

Living The Life

The upgrades on the 2016 Colorado as is now include a modified stock turbo with a BorgWarner S369 as a set of compounds, the lightly modified factory intercooler, Exergy 100-percent-over injectors with other minor fuel upgrades, a RevMax built transmission, PPEI tuning, an ICON 2.5-inch lift kit with FOX shocks, 35-inch Nitto tires on Fuel wheels, and a 4.10-ratio rear axle.

“This truck at its size and power is like driving an 800- to 900hp heavy-duty pickup,” says Josh. “The throttle response and set-you-in-the-seat power is unreal for what you see when you look at the truck!”

Things seemed bleak for a while for the little Duramax, but it overcame all odds and emerged victorious! It now lives a happy life with its owner on a ranch and does everything it’s demanded to.


Automotive Racing Products



Exergy Performance


Fuel Off-Road Wheels


Jag’s Pro Truck Shop

Nitto Tire

PPEI Custom Tuning

RevMax Converters

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