Aim­ing for 1,000 hp in a Du­ra­max street truck

Ultimate Diesel Builder's Guide - - Contents -

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 Mid­dle­town, 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 stock­ap­pear­ing 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.

Soon Casstevens was talk­ing to Chase Fleece and LJ Ben­shoof and Greg Lossi from Free­dom Rac­ing En­gines to get the process started build­ing his block. Us­ing a core LBZ block as a start­ing point, the team at FRE was set to ma­chine and build the short block. With a 0.020-over en­gine bore, cylin­der heads milled with a com­pe­ti­tion valve job, bronze valve guides, FPE max life PSI springs, chro­moly re­tain­ers and keep­ers, Trend Per­for­mance Stage 3 push rods, Car­rillo con­nect­ing rods, Mahle Mo­tor­sport pis­tons, keyed and pol­ished crank, So­cal 3388 cam, ARP main bolts and head studs with Grade C head gas­kets, and all-new Cle­vite in­ter­nal bear­ings, this LBZ was ready to breathe fire.

Back at Fleece Per­for­mance, Casstevens and some of the guys in the shop helped pull some long nights as­sem­bling the en­gine and in­stalling the new heart in the ’07’s en­gine bay. Casstevens and the Fleece team fur­ther tight­ened up the Du­ra­max with an ATI Su­per­damper, new oil pump and oil cooler, PPE ex­haust man­i­folds and up­pipes, ATS Diesel dual pump kit with twin Fleece Pow­er­flo 750 10mm CP3S, Pure­flow Air­dog 200 4G fuel sys­tem, Banks Power Intercooler and a Sun­coast bil­let flex­plate. Then they bolted the en­gine in place with a set of Mer­chant Automotive en­gine mounts. Ex­pelling the fumes from the beast of an en­gine is a 5-inch JAMO ex­haust sys­tem with a 6-inch tip. But even the built en­gine and single S366 tur­bocharger wasn’t enough to quench Casstevens’ thirst for more power.

The next stop on the road to glory was Seth Wal­lace and Jake Bells of BOFA (Build Over­haul Fabri­cate Any­thing) Per­for­mance in Fair­mount, In­di­ana, to cus­tom build a com­pound turbo setup for his GMC. This would be BOFA’S first kit for the Du­ra­max pow­er­plant, but they didn’t back down from the chal­lenge. Af­ter tool­ing and re­tool­ing their fab­ri­ca­tion, the crew was able to craft a sleek and pow­er­ful com­pound setup, sport­ing the S366 turbo as well as an S480. Casstevens’ at­ten­tion to de­tail shined as he made sure to dress up the up­graded en­gine com­po­nents in an elec­tric Il­lu­sion Blue­berry pow­der­coat fin­ish by Shane Marshell at PCT Coat­ings tied in through­out the en­gine bay. With an ex­pert tune by Bray­den Fleece, this LBZ was set to top some charts.

Later, Casstevens up­graded his trans­mis­sion fur­ther to keep up with the power with Sun­coast

bil­let in­put, out­put and in­ter­me­di­ate shafts, bil­let C2 and P2 hubs, mod­i­fied P1 sun gear, and swapped to a Sun­coast 1053 torque con­verter for a higher rpm stall speed. With this con­fig­u­ra­tion, Casstevens was able to put down an im­pres­sive 950 horse­power and 1,765 lb-ft of torque in his street-driv­ing Du­ra­max. And with some even more ag­gres­sive tunes loaded now, he plans to break that cov­eted 1,000-horse­power mark next time he straps the truck down to a dyno.

With all that power cours­ing through the veins of the Sierra, Casstevens had to fo­cus on get­ting it to the street and keep­ing it there. To counter a weak point of­ten found in pow­er­ful GMS, Casstevens in­stalled Fleece Per­for­mance tie-rod sleeves. Tight­en­ing up the per­for­mance truck’s ride are the two-inch Belltech drop shack­les, Bil­stein 5100 front shocks and steer­ing sta­bi­lizer, Cal­trac trac­tion bars, and the re­moval of the rear over­load springs. Hos­tile Havoc 20-inch wheels where se­lected and paired with 305/50 Nitto 420s for grip down the road.

The fo­cus of the build had been to cram im­mense power into a streetable ma­chine, so when it came to aes­thet­ics, Casstevens opted for a sub­tle, sleeper ex­te­rior and com­fort­able in­te­rior. Spencer Baledge in Alexan­dria, In­di­ana, helped color-match the Sil­ver Birch fac­tory paint into the mir­rors, han­dles, and bumper plas­tics for a sleek cus­tom look. A bil­let alu­minum grille with the GMC logo re­moved, aftermarket head­lights, and tint­ing on all three brake lights added some sub­tle touches to catch your eye. In­side, the

fac­tory gray leather re­mains with the only vis­i­ble mod­i­fi­ca­tions be­ing the Au­tome­ter A-pil­lar gauge pod with Ul­tra-lite II gauges and an Edge tuner over­head. Audi­ble cus­tomiza­tion comes from a JL Au­dio 6W3 sub re­plac­ing the fac­tory Bose model in­side the cen­ter con­sole and a JL Au­dio 200-watt amp tied into the sound sys­tem.

All it took was that first up­grade and a lit­tle en­cour­age­ment and Casstevens caught the per­for­mance bug. Even with a lofty goal, he was able to pull to­gether his dream truck with help from friends at Fleece Per­for­mance Engi­neer­ing, BOFA Per­for­mance, Free­dom Rac­ing En­gines, and his brother Jar­ren Casstevens. Liv­ing up to the goal, Casstevens 2007 GMC Sierra 2500 rides like a daily driver—that is, un­til you mash the throt­tle and let the beast come to life. Con­tin­u­ing to prove it can take the street or the track, on a re­cent 200 mile trip with the nearly 1,000-horse­power ma­chine, it av­er­aged 19 mpg. Casstevens truly built an awe­some diesel truck. UDBG

Text : Kyle Tobin Pho­tog­ra­phy: Chris Tobin

Collin Casstevens’ sleek, sub­tle 2007 GMC Sierra hides a mon­strous en­gine caged in­side ready to de­vour any road in front of it.

The S480 at­mo­spheric turbo feeds air di­rectly into the sec­ondary S366 to boost the in­take charge fur­ther be­fore it cy­cles through the Banks intercooler and fi­nally into the LBZ’S in­take man­i­folds.

The Du­ra­max con­fig­u­ra­tion can make it chal­leng­ing to keep a tidy en­gine bay, but Casstevens did it right with pow­der­coated Il­lu­sion Blue­berry ac­cents and out­stand­ing pipe and wiring work.

With the pul­ley pow­der­coated to match the en­gine ac­cents, the sec­ond Fleece Pow­er­flo 750 10mm CP3 stands out as it does its job of pro­vid­ing a high vol­ume of high­pres­sure fuel to the over­sized Fleece in­jec­tors.

With Fleece’s tie-rod sleeves and Bil­stein 5100 shocks and steer­ing sta­bi­lizer, the front end is equipped to hold steady when the po­tent LBZ is un­leashed.

Vi­tal com­po­nents to the high-pow­ered en­gine are the smoothly fab­ri­cated JAMO 5-inch ex­haust (part of which is seen here) and the Pure­flow Air­dog 200 4G fuel pump and fil­ter sys­tem to get plenty of clean #2 up to the dual Fleece CP3S.

BOFA Per­for­mance ex­pertly fab­ri­cated the com­pound setup, which not only looks fan­tas­tic in the stel­lar blue pow­der­coat, but also helps this en­gine get close to 1,000 horse­power and still man­age to be street-friendly.

Af­ter re­mov­ing the rear over­load springs, Casstevens in­stalled Cal­trac trac­tion bars to en­sure the rear end would hook up un­der power. Grippy Nitto 305/50R20 NT420S tires wrap around 20-inch Hos­tile Havoc wheels on all four cor­ners to add some style as...

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