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2003 Chevrolet Silverado 2500 HD - Maximum Power

A 1,300HP, Street-Driven Duramax

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Buck Spruill is a man who is never satisfied. That might explain why he's taken a regular '03 Chevrolet 2500HD with a 300hp, 6.6L Duramax diesel engine, and transformed it into the 1,300-horsepower monster you see on these pages. The road has been long and hard, and he's broken numerous parts along the way, including 40 (that's four-zero) Allison transmissions!

Before we get too deep into the transmission story, we'd better get you up to speed on the rest of the truck. The engine that produces Allison-melting power is based off an '03 LB7 block that has been fortified with aftermarket rods, 15:1 compression pistons, ported heads, a cam, head studs, and valvespring setup, all from TTS Power Systems. Burkett Racing engines performed all of the machine work and engine assembly, and the heads were fitted with O-rings and LBZ valves.

Up top, a Garrett GT4202 turbo provides a whopping 65 psi to the maxed-out engine, while up-pipes from a C4500-series truck, and a 4-inch downpipe provide plenty of exhaust flow in, and out of, the turbocharger. A three-stage NOS Launcher nitrous system was also used, and it has been modified by Buck into a direct-port unit. This way, Buck can inject nitrous into each individual cylinder, controlling EGTs as well as adding an estimated 400 additional horses. Buck also has lots of fuel, thanks to an ATS dual CP3 kit with Industrial Injection CP3 pumps, and Industrial Injection injectors that flow a whopping 100% more than the stock units. Tuning was handled by TTS Power Systems.

With an estimated 1,300 nitrous-assisted horsepower at 4,000 rpm, the truck has been far from reliable. "We'd take it out in front of the farm on a test run and lean on it a little," Buck recalls. "Half of the time, the truck wouldn't make it back to the house."

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