An LML Built to Match its Owner’s Right Foot
When you crack a piston at 94,000 miles, you go all in. At least that’s what Garrett Zumwalt (@gzumwalt) did, a 21-year-old farmer from Silex, Missouri. With an ’05 LLY farmhand available for daily driving and towing duties, it only made sense for him to “officially” transform his ’14 Silverado into a full-time play toy. The LML Duramax is built about as well as you’d need for a truck that’s set up to send 800 to 1,000 hp to the pavement. A built Allison, a healthy fuel system, and an S400 play critical supporting roles in the effort, and the right traction and steering mods are in place, too.
After one of the LML’s eight original pistons bit the dust with nothing more than a tune for a power-adder, Garrett wanted to avoid any type of catastrophic engine failure going forward. Enlisting the help of LinCo Diesel Performance, and with LDP knowing Garrett to be (self-admittedly) a bit hard on things, a host of stronger hard parts were rounded up for the rebuild. Things got started with a factory stroke (3.900-inch) keyed Compstar crankshaft from Callies, with Wagler Competition Products’ billet main caps and ARP main studs securing it within the block. A set of Wagler’s forged-steel Street Fighter rods, complete with ARP rod bolts, attach to coated Fingers oval bowl pistons, and one of Wagler’s keyed Stage 2 alternate fire camshafts sits in place of the factory one. Up top, the heads were treated to a performance valve job at LDP Machine, along with Wagler dual valve springs and ARP 425 head studs.
CP3 Swap & 45-Percent Overs
For utmost reliability, the factory Bosch CP4.2 was done away with. A CP3 conversion kit from Fleece Performance Engineering made the CP3 swap possible, and Garrett opted for Fleece’s PowerFlo 750. The 10mm stroker pump has no issue maintaining rail pressure for the 45-percent over Exergy Performance injectors, even with significant duration brought into the mix. Low-pressure fuel supply is delivered to the CP3 through ½-inch lines spanning to a 165-gph Titanium series FASS system. A drivable, 800 hp is made possible thanks to Danville Performance tying everything together in the LML’s ECM.
Even though he ran a 63mm VGT for a time, uncorking the LML’s true potential meant switching to a bigger, fixed geometry charger. The ideal turbo would come from Stainless Diesel: a 5-blade S468/83/1.0 with a V-band compressor housing outlet and a T4 turbine inlet flange. HSP Diesel supplied the single S400 system, complete with a pedestal, 3-inch diameter intercooler piping, and even the cold air intake. Helping to drive the S400 is a set of PPE’s high-flow exhaust manifolds and stainless steel up-pipes. The 5-blade S400 sends just under 50-psi of boost through the factory intercooler.
Built with plenty of insurance for Garrett’s current horsepower combination, the Stage 5 competition Allison 1000 was assembled at LinCo Diesel Performance. The six-speed benefits from LinCo’s proprietary clutch kit made up of a mixture of Sun Coast SCZ clutches. Billet hard parts include Xcalliber billet input, intermediate, and output shafts, along with Sun Coast’s billet C2 hub and P2 planetary. To bring the S468 to life quickly, a 1055-2, high-stall (2,400 to 2,600 rpm) triple-disc Sun Coast converter is employed, while a Fleece AlliLocker provides full control over lockup.
A horsepower junkie to the core, right about the time Garrett’s truck clears 800 hp on the chassis dyno he plans to tear into the engine again, add 150-percent over injectors, a 14mm CP3, a bigger S400, and pursue four-digit horsepower. With plans to hit a few Midnight Madness events at the local quarter-mile—along with hooking it to the sled—this summer, you’ll either find Garrett putting the truck’s driveline to the test in the dirt, or somewhere in the 11’s at the drag strip.