Chasing Horses: How Katie’s Duramax hit over 1000hp

May 2017 Duramax, Power of Pink, Feature Austa Cook

This article originally appeared in the May 2016 issue.

“Growing up, I was always in the garage with my dad,” Katie Pajestka says. This Minnesota girl was raised learning to drive an old beater first generation Cummins, and this was how her father taught her and her sisters how to know their way around a truck.

“All of us were raised to know what was under the hood. Not that I'm a mechanic in any way, but my dad raised my sisters and me to know how to do the basics so we didn't have to rely on anyone,” Katie explains.

When Katie purchased her own diesel when she turned 18, she decided to stick with the familiarity of a Cummins—but in less than a year, fate struck when she had her first experience climbing behind the wheel of a Duramax.

“I instantly fell in love with a Duramax engine and GM trucks overall,” Katie enthuses. “The GMC fit my personality a lot better. I purchased my 2003 LB7 in 2009 and have been making modifications ever since.” 

Though she uses her truck as a daily driver, Katie also got involved in drag racing. At that time, her truck ran an 11.8-second quarter mile.

“After that, I decided it was time for a full build,” Katie explains.

Setting Goals

When you see how long her next list of mods stretches out, you’ll begin to realize just how much Katie has poured her heart and soul into this ever-evolving build. That’s in part because she had her sights set on a serious goal—to hit 1000 horsepower.

Katie enlisted the help of Jason Wehrli, owner of Wehlri Custom Fabrication, and Nick Priegnitz and Bob Peterson, owner and tuner at Calibrated Power/Duramax Tuner, respectively, in selecting the right list of modifications to reach this achievement.

“After months of planning and discussing my horsepower goals we came up with our build plan,” Katie says.

And the work began.

Her engine was built by Wehrli Custom Fabrication, where the team installed Fingers Oval Cast Mahle .020 Pistons with a 16.5:1 compression ratio and valve reliefs. Ported heads, a 5-angle valve job, pushrods, and new seals and guides were also added to the list. Katie invested in COMP Cams valve springs and retainers, and installed Carrillo rods to ensure long-lasting integrity in her connecting rods. ARP rocker arm bolts and head studs were paired with Merchant Automotive motor mounts and backed up by the SoCal engine girdle kit to tie the main bearing caps and oil pan rail together for increased block rigidity. The SoCal 9100 AF camshaft toughened up the crankshaft and SoCal billet injector hold downs were added as insurance against injector lifting. The SoCal Damper was installed to prevent adverse engine harmonics.

And The List Continues

A new GM Oil pump and cooler and new Exergy 150 percent injectors were joined by other upgrades like screw-in injector cups, a DRP Fuel Sump and AirDog II-4G fuel system. The PPE manifolds and cooler, dual CP3s, a WCFAB compound turbo kit, and WCFAB 2-inch stainless up pipes all make for big air flow and efficiency, and the OldSkoolFab Carbon Fiber Stack shows off the right attitude to back up the growing power of this engine. Katie’s engine was EFILive Tuned by Duramax Tuner/Calibrated Power.

As far as front end and suspension work goes, Katie invested in Rancho 9000 shocks, a PPE straight center link, and Flight Fabrication Traction Bars to help distribute torque through the body’s frame. To fortify the inner tie rods against bending, Katie added tie rod sleeves from Merchant Automotive. She also lowered her truck 3 inches with Belltech drop shackles to cut down on air drag during races.

Katie also ramped up the style of her interior with black-faced, white-backlit Isspro gauges. She added a BT DieselWorks digital DSP5 gauge pyro to go with her fuel rail pressure, trans temperature gauge, and two boost gauges. Finally, Katie invested in BMF Rehab 20x10 wheels and wrapped them in sporty 305/50 Toyo Proxes.

“This Duramax has been through so many changes, it’s hard to keep track,” she laughs. “Bob spent more time in my truck than anyone. He did the engine break-in and made sure that everything was perfect for me. Bob and Nick are tuning geniuses!”

Holding Power

Last but not least, her transmission underwent a complete billet build by Merchant Automotive. This included upgrading to SunCoast GMAX5 clutches, a billet flexplate, ARP’s flexplate bolt kit, a C2 hub, and billet input and output shafts. The DRP upgraded tranny lines round out the job.

“Justin, Nick, and Bob and their shops are in my opinion the best in the industry!” Katie says. “I am more than happy with the outcome of what these two shops put together for me.”

So now the big question—did these modifications help Katie hit her lifetime goal of 1000 horsepower?

Not only did she reach it, she beat that goal by 33 horsepower.

“It's more than I could have ever imagined,” Katie grins. “The work put into my truck demonstrates how professional WCFAB and Duramax Tuner are. Without them and the encouragement of my boyfriend, this build wouldn't be possible.”

Ready For The Season

When her truck was dynoed after all of this work, it reached a very impressive 1033hp and 1973 ft/lbs. of torque. Needles to say, Katie is excited to hit this year’s race season hard.

“I'm hoping to be able to run a 10.5 in the quarter mile,” she says. 

Though her heart is taken with drag racing, Katie did get to sled pull for her first time last year and will definitely do it again this year.

“It's a different kind of adrenaline rush, that's for sure,” she enthuses.

Between racing and pulling, however, this beastly build still remains a steadfast daily driver, and Katie couldn’t be happier with it.

“Stick to your guns and don't let anyone bring you down,” Katie says. “Continue to do what you're passionate about, whether it's drag racing, sled pulling or just modifying the looks of your truck.” To the diesel ladies out there, Katie adds, “As women, we need to help each other, not hurt each other. We need to stick together and prove that just because we're women doesn't mean we can't all enjoy what we all have grown to love.”  

Photos by Becka Vaughan



Automotive Racing Products


Belltech Sport Trucks




BT DieselWorks


Calibrated Power Solutions/Duramax Tuner 


Calvert Racing Suspensions




Comp Cams


Deviant Race Parts


DJM Suspension


Exergy Performance 


Flight Fabrications


General Motors




Merchant Automotive




PPE Diesel Performance




SoCal Diesel


SunCoast Diesel Transmissions


Toyo Tires


Wehrli Custom Fabrication 



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