Andrew Murdoch thought he paid a reputable shop to turn his ’03 GMC Sierra into a high-horsepower monster. What he got instead was a horrible mess. When an incorrectly ported cylinder head cracked and allowed coolant to flow into the combustion chamber, his brand-new (and expensive) built motor was ruined. Diagnosing the Duramax’s failure was a nightmare because almost every sealing surface on the drivetrain leaked. The transfer case was the only exception—but that was because nobody had ever refilled it with ATF. Taking the devastated engine apart was easier than you’d think, because upon beginning the initial teardown, Andrew found out his Duramax’s valve covers were cracked, and many of the bolts were missing. The engine wasn’t a total loss, but it was close. Duramax Redo: Round Two None of us would have blamed Andrew if he had given up on diesel performance at that point. After such a horrific experience, he could have just walked away from his dreams, returned the truck to stock, and cut his losses. But he didn’t. Nope, after a series of emails, phone calls, and private messages, Andrew got in touch with Newly Tolf at Underground Diesel in Las Vegas. The two men discussed what had happened to the truck, the condition of the parts, and the cost of doing the job right. When Tolf got off the phone, he hitched a trailer to the back of his C4500 and drove to Colorado to personally pick up Andrew’s GMC. When the truck was rolled into the shop, Tolf’s staff immediately set to work on righting all the wrongs that had been done to this ’03 ¾-ton. After a few weeks, the test fitting of a few prototype parts, and a compound-turbo kit install, Andrew’s LB7 Duramax rolled back out of the shop—but this time under its own power. Right before Andrew flew into town to pick up his second-chance Sierra, Tolf took us for a cruise in the truck on the Vegas strip so we could witness firsthand what a twice-built Duramax diesel can do. This LB7 Duramax has Carrillo rods; Mahle 0.020-inch-over pistons; a SoCal camshaft; a Performance Diesel Machine (PDM) Gorilla Girdle (ties in main bearing caps); a polished, re-nitrided, and keyed crankshaft; ARP main and head studs; SoCal injector hold-downs; and a SoCal Super Damper. The powdercoated Underground Diesel compound turbocharger setup is based on MPI S366 and 480 turbos with billet compressor wheels. PPE race manifolds and up-pipes and a Banks intercooler handle the added boost. A PPE coolant tank and oil centrifuge help manage the fluids. A PPE Dual Fueler CP3 pump and DDP 100 competition nozzles provide plenty of fuel. Merchant Automotive motor mounts and its welded water pump keep everything together.This LB7 Duramax has Carrillo rods; Mahle 0.020-inch-over pistons; a SoCal camshaft; a Per Performance Diesel Machine performed a Stage 2 CNC porting job on the Duramax heads’ exhaust and intake runners. It also added 95-ft-lb springs and its new screw-in injector cups.Performance Diesel Machine performed a Stage 2 CNC porting job on the Duramax heads’ exhau The AirDog II has a pressure setting that is adjustable. This Duramax in its factory form didn’t come with a lift pump.The AirDog II has a pressure setting that is adjustable. This Duramax in its factory form Here is the switch that controls the different tunes on the EFILive tuning. This truck also got the Fleece Performance Allison Tapshifter conversion.Here is the switch that controls the different tunes on the EFILive tuning. This truck als The oil return line for the second turbocharger was tapped into the aluminum oil pan above the oil fill level for proper drainage. When drilling the pan to install this fitting, it’s recommended that you add an extra quart of oil to the engine so the added capacity will push all the shavings from the hole.The oil return line for the second turbocharger was tapped into the aluminum oil pan above It rolls on 20x10-inch Fuel Hostage rims and 305/55R20 Falken Wildpeak A/T tires. Merchant Automotive transmission lines, a PPE Stage V transmission with deep pan, PPE PTO covers, and a Mike L. cooler handle the power going to the wheels.Merchant Automotive transmission lines, a PPE Stage V transmission with deep pan, PPE PTO The transfer case support brace keeps the drivetrain solid—even under high-horsepower shifts.The transfer case support brace keeps the drivetrain solid—even under high-horsepower shif PPE overhead gauges measure boost and fuel rail pressure. The interior features a Kenwood entertainment system along with multiple speakers and subwoofers (under the seat).PPE overhead gauges measure boost and fuel rail pressure. The interior features a Kenwood Cognito upper control arms, Bilstein 5100 shocks, and a PPE idler-arm support kit fortify the GM IFS torsion bar frontend.Cognito upper control arms, Bilstein 5100 shocks, and a PPE idler-arm support kit fortify The exhaust tip comes from RBP, and the aluminum differential cover was made by PPE. Merchant Automotive traction bars keep the wheels from hopping when the power gets put to the wheels.Merchant Automotive traction bars keep the wheels from hopping when the power gets put to By Jason Thompson Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!