Uncharted Waters

Colton Rhodes’ 1,000HP L5P Breaks All The Rules

Big single, CP3 conversion, sizeable nozzles, and a bone-stock long-block…what could go wrong? Welcome to Colton Rhodes’ world. The 20-something Missourian is redefining what it means to push the limit—and he’s doing it every time he cycles the ignition of his ’17 Silverado. The L5P Duramax under the hood has gone completely untouched despite receiving a host of fuel and air upgrades—and the built-to-the-hilt Allison behind it means the transmission is never going to be a weak link. His reasoning for the apparent death wish for the engine is simple: if you don’t push the limits, you’ll never know how much you can get away with. Plus, when you “know a guy” with a machine shop, it doesn’t exactly act as a throttle stop.

Stock As A Rock

Did GM’s new casting and additional heat-treating processes truly improve the strength of the L5P’s gray-iron block? Will the 20-percent larger rod bearings really help them live at higher horsepower? And can the thicker walled pistons it’s said to have survive the cylinder pressure that comes with 1,500 lb-ft of torque? Colton will get back to you on that, but so far so good. The seal has yet to be broken on his 110,000-mile Duramax, and he doesn’t plan to pull the valve covers until something gets hurt. Not even the head bolts have been swapped in favor of ARP studs at this point. It’s simply been full speed ahead.

DW-2105-GMGRAY-02 — The first thing you notice under the hood is that the factory VGT went into early retirement. However, what you don’t see are the 150-percent over injectors, the CP3 conversion, and the 12mm CP3 from S&S Diesel Motorsport. As for the long-block, it’s 100-percent stock—not even the head bolts have been replaced with studs. Some might call it rolling the dice, but Colton calls it R&D. He’s pushing the limits of the factory L5P to see just how much you can get away with before something cracks, pops, or explodes. No matter what happens, Colton knows a guy with a machine shop, so he isn’t exactly worried about engine carnage.

The Denso HP4 and factory in-tank lift pump are the latest and greatest in fueling, making for solid potential right out of the box on the L5P, but there was no way they were going to support the kind of power Colton sought after. A CP3 conversion from S&S Diesel Motorsport allowed one of S&S’s 12mm pumps to replace the HP4 in the factory location. For low-pressure fuel supply, a Titanium Signature series FASS system was added, and its 220-gph flow rating ensures the CP3 will never run dry. The factory solenoid style Denso injectors were pulled and sent to S&S for 150-percent over nozzles and a few of the company’s in-house modifications.

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An S472 With Manners

Despite Colton having no reservations about pushing the stock bottom end to the brink, there is no denying that a single turbo—and a fixed geometry unit at that—is much easier on hard-parts than compounds, or even a large VGT. Armed with this common knowledge, he decided to run an S472, which was made possible thanks to HSP Diesel’s S400 single turbo install kit. But instead of having a power curve that comes on like a light switch, the big single was sourced from Stainless Diesel, a turbo manufacturer that’s known to build some of the most drivable S400’s in the industry. At Stainless Diesel, the S472 was treated to the company’s 5-blade billet compressor wheel, an 87mm turbine wheel, and also fitted with a 1.0 A/R exhaust housing.

DW-2105-GMGRAY-03 — Ditching the factory VGT was made possible thanks to an S400 single turbo install kit from HSP Diesel. The T4 pedestal, intercooler tubes, and cold air intake accommodate an S472 from Stainless Diesel. Equipped with a billet, 5-blade compressor wheel, 87mm turbine, and a 1.0 A/R exhaust housing, the big single makes just under 50-psi of boost at full tilt.

Built Allison and Traction Upgrades

As expected, the Allison was one of the first components to benefit from upgrades. For a full-on, competition-ready build, LinCo Diesel Performance got the call. In its care, the six-speed was fitted with Sun Coast-sourced billet input, intermediate, and output shafts, Sun Coast’s P2 planetary and billet C2 hub, and LinCo’s proprietary clutch packs. A high stall (2,800 to 3,000-rpm), 1071 Sun Coast triple-disc torque converter helps bring the S472 to life quickly, and a deep pan from PPE adds four quarts of fluid capacity. With the Allison ready to handle anything the L5P could dish out, Colton added Kryptonite tie-rod sleeves before attempting the first four-wheel drive launch—along with adding a set of LinCo’s bolt-on traction bars to eliminate rear axle wrap.

DW-2105-GMGRAY-05 — Built at LinCo Diesel Performance, the Allison 1000 is chock full of the best parts Sun Coast has to offer. Better yet, as a reward for being one of the largest Sun Coast transmission dealers in the country, every component but the billet intermediate shaft was donated to LinCo for the build. To hold up to four-digit horsepower, a billet input, the aforementioned billet intermediate, and billet output shaft made the cut, as did a billet P2 planet, C2 clutch hub, and LinCo’s proprietary mix of clutch packs. A 1071 model Sun Coast triple disc converter with a 2,800 to 3,000-rpm stall speed helps bring the S472 to life quickly.

DW-2105-GMGRAY-06 — To quell axle wrap and leaf spring twist, Colton runs a set of LinCo Diesel Performance traction bars. Bolt-on frame and axle mounts, along with heat-treated chromoly heim joints provide for plenty of rigidity without any banging and clanging.

DW-2105-GMGRAY-07 — Stiffening up the IFS’s steering system, a set of zinc-plated, solid-steel Kryptonite tie-rod sleeves were threaded onto the factory tie-rods. So far, this is the extent of the truck’s steering mods, but it’s arguably the most important addition you can make on any heavy duty GM.

DW-2105-GMGRAY-04 — Being based just 30 miles from FASS fuel system’s Marthasville, Missouri headquarters has its benefits. When the company was looking for a demo truck for developing a system for the L5P, Colton offered his Silverado up for the cause. As a result, he walked away with one of FASS’s 220-gph systems—plenty of fuel supply for the 12mm CP3.

Constant R&D

As Colton continues to work with the experts at CTT Tuning to dial everything in electronically, he’s been racking up plenty of miles (many of which are hard-earned) on the new setup. Should any engine issues arise, the L5P will be treated to a SoCal cam and ported heads, along with ARP head studs, during a rebuild. Whether the engine remains completely stock or sees a complete race-ready overhaul between now and summer, he plans to visit the drag strip and even hook to the sled a few times once the weather warms up. Call it fearless, call it cocky, call it whatever you want, but Colton is performing the kind of R&D that will only serve to drive the industry forward.

DW-2105-GMGRAY-08 — Even though the 305/55R20 Dick Cepek Trail Country EXP’s—mounted on 20×10 Hostile Vulcan wheels—sometimes struggle to grab ahold of the road, the truck looks darn good doing it. Colton’s subtle taste in a wheel and tire combo flows well with the overall theme of the build. Nothing is over-the-top—even though the truck’s performance is about as serious as a heart attack.

DW-2105-GMGRAY-09 — For the truck being in rough shape when Colton got his hands on it, you would never know it. Despite having 100,000 farm miles thrown at it in just three years, the interior is essentially flawless.

DW-2105-GMGRAY-10 — An Insight CTS3 monitor from Edge meshes perfectly with the latest GM interior, and it allows Colton to keep tabs on the truck’s vitals. Rail pressure, transmission temp, and boost are among the key parameters he likes to glance at from time to time.

“Call it fearless, call it cocky, call it whatever you want.”

DW-2105-GMGRAY-11 — If you thought zero in-fighting occurred within the confines of the Duramax world, think again. Colton’s friendly rivalry with Garrett Zumwalt and his 800hp LML (left) has yielded no signs of cooling down—especially now that Colton’s L5P is packing four-digit horsepower.

DW-2105-GMGRAY-12 — Back when the truck was closer to stock—though it still had a 63mm Danville drop-in VGT and hot tuning—Colton hooked his Silverado to the sled. When he returns to the dirt this summer, his L5P will be packing four-digit horsepower and should move the iron sleigh much further and faster.

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Holy Grail

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Hritik Godara

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