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2006 GMC Sierra 2500HD - All Business

Black-on-Black, Compound Turbos, 750HP

Mike McGlothlin
Dec 17, 2014
Photographers: Mike McGlothlin
For a lot of us, the diesel addiction came naturally. For others, it developed over time. John Zibutis, a former minitruck and street-bike enthusiast, fell into the latter category. He started to take an interest in diesel trucks roughly eight years ago, when oil burners began to explode with popularity. “I got into diesels once the trucks rode better, actually made power, and GM built an engine that didn’t have a ton of problems,” he told us. He then quickly added, “But I never thought I would go this far with my Duramax.”
Believe it or not, the ’06 GMC Sierra 2500HD you see before you was pampered the first 36,000 miles of its life, and John’s father was its second owner. But after his father lost his bout with cancer in 2008, the keys were left to John—so it goes without saying that there is a lot of sentimental value involved with this ultra-clean GMC.
While an Edge Juice with Attitude programmer (uploaded with the Hot Unlock tune, of course) proved fun and put the truck at the 460hp level at the rear wheels, John wanted more out of his GMC’s 6.6L LBZ engine. Taking the advice of his friends, he bit the bullet and tackled the unavoidable job of fortifying the Allison 1000 automatic transmission before adding big power. For the bulletproof build, he took the truck to Flynn’s Shop in Alexander, Illinois, where the six-speed automatic was fitted with a GMax 6-pac clutch kit, a TransGo shift kit, and a 1058 torque converter from SunCoast. For added insurance, a pump rub kit and transfer case brace from Merchant Automotive were also installed.
Photo 2/15   |   The 6.6L LBZ Duramax resting in John Zibutis’ ’06 GMC Sierra is far from stock. A Fleece Performance Engineering short-block houses forged-steel Carrillo rods, Mahle cast-aluminum (and coated) 16.5:1 compression pistons, and a SoCal Diesel 3388 cam. Top end mods were performed by Flynn’s Shop, where double-spring valvesprings from Diesel Technology Source and Custom Age ARP head studs were utilized.
With the slushbox complete, it was full steam ahead on the engine. A set of Exergy Engineering injectors with 60-percent-over nozzles replaced the stockers, the factory CP3 injection pump was pulled and transformed into a 10mm stroker pump at Motorsport Diesel, and a 68mm Cheetah turbocharger from Fleece Performance Engineering was added. ARP 2000 head studs would also be threaded in one at a time to keep the heads from lifting.
Knowing he was playing with fire at the 650hp mark (where the LBZ’s factory pistons are known to crack), John pressed on, adding a stock-over-S475 twin-turbo kit from Duramaxtuner.com. A few thousand miles later, theinevitable occurred: a cylinder misfire and white smoke billowing from the tailpipe. However, instead of throwing in the towel, John decided to go all out and contacted Fleece Performance for a built short-block. The competition-ready bottom end consists of Carrillo rods, Mahle coated pistons, and a SoCal Diesel camshaft. The cam, crankshaft, and water pump are all keyed. Flynn’s Shop took over the assembly from there, fitting the heads with Diesel Technology Source valvesprings and securing them to the block with Custom Age ARP studs.
Photo 3/15   |   Shortly after our interview, we found John and his truck doing this. At roughly 7,200 pounds, a 92-mph trap speed in the eighth-mile confirms this nasty GMC is making at least 750 hp at the wheels.
Also going bigger in the fuel and air department during the rebuild, John had Flynn’s upsize the compound-turbo arrangement considerably with a 220-gph Titanium Series fuel system from FASS. Replacing the factory Garrett ’charger in the valley is a 68mm PowerMax (GT4094VA), while an S480 now resides where the S475 used to.All turbo plumbing came from Wehrli Custom Fabrication. The EFILive gurus at Duramaxtuner.com dialed in both the ECM and TCM, which makes for an exceptionally clean, fun-to-drive truck on the street.
While John has indulged in several different gearhead-type hobbies over the years, we think his passion for diesels is here to stay. Case in point: He’s already drawing up plans to make more horsepower this winter. His wish list includes dual CP3s, 100-percent-over injector nozzles, EFILive tuning, and at least 850 hp at the wheels—and John is the kind of guy who always gets what he wants.
Fast Facts:
Year/Make/Model: 2006 GMC Sierra 2500HD
Owner: John Zibutis
Hometown: Sherman, Illinois
Odometer: 52,000 miles
Engine: 6.6L Duramax LBZ, forged Carrillo rods, castaluminum Mahle (coated) pistons, SoCal Diesel 3388 cam, Diesel Technology Source valvesprings, ARP Custom Age head studs
Fuel: FASS Titanium Series 220-gph fuel system, FASS fuel sump, Motorsport Diesel 10mm stroker CP3 injection pump, Exergy Engineering 60-percent-over injectors
Air: GT4094VA/S480 compound turbochargers with Wehrli Custom Fabrication plumbing
Transmission: Allison 1000 automatic built by Flynn’s Shop with SunCoast GMax 6-pac, TransGo shift kit, and SunCoast 1058 torque converter
Horsepower: 750 hp (track)
Tires: 305/50R20 Nitto NT420S
Wheels: 20x10-inch BMF Novakane
Suspension/Sterring: Exaxt chromoly tie rods, pitman and idler arms, and centerlink