Got The Bug
Ultimate Diesel Builder Guide|June-July 2017

Collin Casstevens aims for 1,000 horsepower with his 2007 duramax street truck.

Kyle Tobin 

How many of us have bought a truck thinking, “I’ll just do exhaust and a chip?” How many of us have actually stopped there? Collin Casstevens from Middle-town, Indiana, had the same idea when he bought his 2007 GMC Sierra 2500—until he caught the diesel performance bug and saw the possibilities. Working at one of diesel motorsport’s hubs at Fleece Performance Engineering at the time of the build, and now as a machinist for Neturen USA, the 21-year-old Casstevens well knew the potential inside his Duramax, and the idea of a 1,000hp street truck was too much temptation to pass up. With the help of several of the industry’s top shops and their best components, he set out to overhaul his daily driver into a road warrior.

After Casstevens initially did his exhaust work and a tune, he felt compelled to give the truck a little more. Once he had bolted on a stock appearing Fleece Cheetah turbo, upgraded CP3 and new injectors, he realized he was going to have to bolster his stock Allison transmission to handle the power he was making with the upgraded Duramax. Jacob Richards at Fleece helped Casstevens tear into the transmission to install a SunCoast Diesel 6Pac kit with Raybestos clutches, Transgo Jr. shift kit, a SunCoast Diesel 1058 billet triple-disc torque converter, Fleece Performance AlliLocker, and Merchant Automotive’s Pump Rub upgrade and transfer case brace. With his newly rebuilt transmission, the truck seemed like a complete build—until Richards said, “You should be good to go now, unless you want to build the motor.” All it took was that seed of an idea to get Casstevens’ mind churning, envisioning a 1,000-horsepower street beast.

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