The Road Was Long, But This 1,000HP LML Was Meant To Be

Ups and downs are part of any major automotive undertaking. However, some projects seem destined to fight you every step of the way. The latter certainly appeared to be true for Cory Jarriel and his LML Duramax. At every turn, the truck seemed to have different plans than he did. First, the truck fell off his two-post lift. Then, after considerable body work, came the electrical fire under the hood, followed by a factory connecting rod vacating the block. Then, once the new engine was in, the supposedly-built Allison sidelined the truck in less than 4,000 miles. Throughout each setback, Cory—who has personally undergone two open-heart surgeries—kept his head-up and ultimately persevered. His reward? A show-ready (and reliable) ’13 Silverado 2500 HD packing four-digit horsepower and more than 2,100 lb-ft of twist.

The Wagler Touch

When it came to the new LML (block and all), very few stones were left unturned. While Cory didn’t opt for a girdle or billet main caps, he did enlist Wagler Competition Products to build his Duramax. The rotating assembly consists of an externally balanced Callies forged-steel crankshaft, its mains secured via ARP studs, Wagler’s forged-steel rods, and fly-cut Mahle Motorsport cast-aluminum pistons. Valvetrain upgrades include Wagler’s alternate firing order cam, chromoly pushrods, and dual valve springs, with the heads being fastened to the block by way of ARP head studs. A Fluidampr, Sun Coast billet flex plate, and a pinned oil pump from Wagler also made it into the build.

When a factory connecting rod left the LML’s block somewhere near the 650-rwhp mark, Cory Jarriel pulled out all the stops when it came to building a new engine. In need of a Duramax that could withstand making four-digit horsepower, he turned to the folks at Wagler Competition Products. A Callies forged-steel crankshaft, ARP main studs, Wagler’s forged rods, Wagler-modified cast-aluminum Mahle Motorsport pistons, and one of the company’s alternate firing order camshafts reside in the crankcase. The heads were fitted with Wagler’s dual valve springs and anchored to the block via ARP head studs.

S369/S480 Compounds

In his quest for a set of compounds that would support 1,000 hp at the wheels, Cory settled on a system from Screamin’ Diesel Performance. The arrangement locates a T6, billet compressor S480 and its corresponding piping on the passenger side of the engine, and replaces the VVT in the valley with a T4 S369 SX-E. High-flow exhaust manifolds and stainless steel up-pipes from PPE help drive the S369 efficiently, while 3-inch hot and cold-side intercooler piping, a Mishimoto intercooler, and a 3-inch Y-bridge open up flow and cool off the air on the intake side.

The engine’s compound turbo arrangement was sourced from Screamin’ Diesel Performance. The system positions a T6, billet compressor wheel S480 out front as the atmosphere charger, an overflow tank behind the passenger side battery, and utilizes 3-inch intercooler piping throughout.
In the valley, you’ll find an S369 SX-E perched atop a T4 pedestal. PPE ceramic coated exhaust manifolds and stainless steel up-pipes help drive the S300’s 73/80mm turbine wheel—a combination Cory says dropped peak EGT by 200 degrees. The twice-compressed intake air is crammed through a Mishimoto intercooler before entering the heads through a 3-inch Y-bridge.

Four-Digit Fueling

Bringing plenty of fuel to the party, Cory sent the stock piezo injectors up to Exergy Performance to be transformed into a balanced set of 100-percent over units. To guarantee the rails never run dry, he elected to run two high-pressure fuel pumps. And thanks to ATS Diesel’s twin fueler injection pump system, a belt-driven CP3 shares fuel pressurizing duties with a CP4.2 mounted in the stock location. A Fuelab Velocity 200-gph lift pump and  -inch fuel lines are responsible for maintaining 8-psi of low-pressure fuel supply for the CP3 and CP4.2 to use. Fine-tuning of the potent injection system is accomplished through the use of EFI Live software.

To support an all-out effort from the 100-percent over injectors that came from Exergy Performance, Cory opted for ATS Diesel’s twin fueler injection pump system. A tried and true, stock displacement Bosch CP3 is belt-driven up top, and a factory Bosch CP4.2 sits in the factory location. Together, the two pumps have no problem keeping the piezo injectors happy.


Billet Allison

After his first “bulletproof” transmission self-destructed in short order, Cory made sure the next Allison build was executed with the best parts on the market. Billet input, intermediate, and output shafts, a billet C2 hub, competition frictions and steels, and a billet stator triple-disc converter from Diesel Performance Converters all made the cut, along with Goerend Transmission’s billet PTO covers, which improve lubrication of the C3 clutches. Extra fluid capacity comes in the form a Mag-Hytec deep transmission pan. The latest reinforced version of his six-speed automatic has proven much more reliable, which, in passing 2,170 lb-ft of torque on to the rear wheels, is saying something.

A Fuelab Velocity 200 lift pump ensures plenty of low-pressure fuel is always on tap for the CP3 and CP4.2. The 200-gph-capable DC brushless motor pump keeps a steady 8-psi worth of pressure heading their way at all times, along with plenty of volume thanks to its ½-inch diameter hose.
After the original “built” Allison lunched itself inside of 4,000 miles, Cory got more involved with the transmission side of things. This version sports a billet C2 hub,  a billet stator, triple-disc DPC converter sitting on a billet input shaft, and billet intermediate and output shafts. Goerend billet PTO covers provide improved C3 oiling and a Mag-Hytec deep pan offers increased fluid capacity.

Curb Appeal & Steering Upgrades

Cory’s Silverado gets its height from a McGaughy’s suspension lift, which provides roughly 9 inches of added elevation up front and 7 inches in the rear. Fox 2.0 remote reservoir shocks (four up front and two in the rear) aid ride quality, and Cognito Motorsports’ alloy series tie-rods and idler and pitman arm support kit reinforce the steering system. Cosmetically, the truck wears the factory Mocha Steel metallic paint, but Cory knocked down some of the shine with satin clearcoat from Vintage Flatz. To avoid the inevitable rock chips that come from running 16-inch wide wheels and large void mud terrains, the rockers were coated in Line-X, along with the sideview mirrors, hood louvers, and grille.

Clearing 35.5-inch diameter, 15-inch wide mud terrains comes easy thanks to a suspension lift from McGaughy’s. It gives Cory’s late-model Silverado 9-inches of available lift up front. Notice the dual Fox remote reservoir 2.0 shocks he went with, along with the Illusion Purple powder coat (more on the powder coating later).
The big Chevy’s AAM 9.25 IFS received steering improvements in the form of Cognito Motorsports’ beefy alloy series tie-rods, as well as the company’s idler and pitman arm support kit. As for the frame, Cory removed all of the factory wax coating that’s prone to peeling and then repainted it flat back from front to back.

The Payoff

It might’ve taken Cory longer to reach his goals than he would’ve liked to, but with the truck running strong and reliably with 1,000-rwhp on tap that’s all behind him now. “I’ve raced an AMG E 63 S and Nissan GT-Rs and won,” he told us. “That’s the fun part about all of it. No one ever expects a big, heavy diesel to beat them.” Tens of thousands of other truck owners, including us, would agree. The diesel thing isn’t the cheapest or easiest hobby to be involved with, but once you get the right combination of parts together it can be one of the most rewarding.

Nothing says aggressive quite like a set of mud terrains, and Cory’s 375/45R22 Nitto Trail Grapplers definitely do the trick. The pavement-friendly M/T’s are mounted on 22×16-inch FF19 gloss-black, forged-aluminum wheels from Fuel Offroad.


“I’ve raced an AMG E 63 S and Nissan GT-Rs and won.”

An Edge Insight CTS2 allows Cory to keep an eye on the LML’s vital signs. He’s happy to report that EGT rarely crests 1,400 degrees—a testament to sound EFI Live tuning and the rest of the truck’s solid parts combination. On the dyno, the Silverado made just shy of 1,000-rwhp and an earth-moving 2,170 lb-ft of torque


To keep the leaf springs from twisting and the AAM 1150 under control out back, a set of McGaughy’s 60-inch traction bars are employed. As for the Illusion Purple powder coat, after being disappointed by the lack of quality he had encountered in the aftermarket powder coat work he came across, Cory built his own oven at his home and started doing his own work. As a result, he powder coated everything you see on the truck, including the leaf springs and U-bolts, traction bars, control arms, shocks, brake calipers, intercooler piping, and even the custom-made rear driveshaft.



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