You know they used to say that what won on Sundays would sell on Mondays. Well, in the case of Matt Moon and his 2002 GMC LB7 Duramax, that statement still applies. Except this all-purpose Sierra is usually racing on Friday, pulling on Saturday, towing on Sunday and working on Monday.
As a long-time employee at Gillett Diesel Service in Bluffdale, UT, Moon has come to learn a thing or two about diesel performance. When you're answering phones and talking with customers about every aftermarket performance product under the sun, you need to know what you're talking about. In Moon's mind, there was no better way to gain that knowledge than to start using the stuff he sold on a daily basis in his own pickup. This '02 GMC has since become a dominant force in the United Truck and Tractor Pulling series across the mountain west states and it's turned out to be a pretty competitive truck at the drag strip and dyno events as well.
In talking with Moon, it's easy to see his true passion is in the truck pulling, as this truck has been meticulously built-up to compete in the 2.8 Super Street pulling class. Like any other competitive daily-driven pulling truck, the road to here hasn't been easy.
The LB7 Duramax motor under the hood was the first stepping stone in this build, as major horsepower would be needed if Moon wanted to begin chasing down the 12V Cumminses at the pulling track. The motor was pulled and built from the ground up by Moon. The crew at Gillett Diesel Service (GDS) modified the pistons and cut a custom keyway in the crank before assembling the block with Crower billet connecting rods. ARP main and head studs were used to hold everything together. The injector studs, billet injector hold downs, hi-rev spring kit and cam all came from SoCal Diesel. Any good motor build starts with proper machine work, so the guys at Randy's Engine and Machine were called upon for their expertise. Randy's did all the block work, including porting and assembling the heads and even balanced the entire rotating assembly once the long list of aftermarket parts was put together.
Once the short block was assembled, Dynomite Diesel injectors were installed, fed by PPE's dual fueler CP3 kit. A BD Power high flow exhaust manifold was bolted on to replace the restricted factory unit as well. GDS has been in the turbo building market for a long time, so Moon knew they could come up with the perfect charger for ultimate airflow while still complying with local 2.8-inch inducer pulling class rules. A Garrett GT4202R was built in-house to meet the strict 2.8 compressor rules, without hindering performance.
With the motor modifications done it was placed back in the truck and a Magnaflow 4-inch exhaust into a 6-inch single stack was mounted up to expel gasses from the large lung that now found itself sitting atop the motor. A Fass 200 gph fuel system is used to supply fuel for the PPE dual CP3 kit at DDP injectors. Tuning is supplied through EFI Live software that Moon continues to improve as more time is spent behind the wheel. An Edge Juice with Attitude monitor is installed in the truck as well, offering great performance adjustability.
The next step in the build-up was trying to plant the new power to the ground, whether it be a dirt pulling track or sticky pavement at the drag strip. Moon built the Allison transmission in-house at GDS using Suncoast internals, converter and a Mag Hytec deep transmission pan was added. The front end was beefed up with an ARB air-locker, tie-rod sleeves, Cognito braces and a Mag Hytec differential cover was bolted on. Out back the rear differential is still using the stock gear train, but a Mag Hytec cover is also bolted on to help keep oil temperatures low. The lift to clear Moon's 35-inch Toyo mudder tires comes from a 6-inch RCD lift with Bilstein shocks. A set of rear airbags, traction bars and adjustable bump stops help with traction as well.
Moon has become known around our office as the man of many tires as he admitted to owning five sets of tires, all mounted and balanced on their own rims, ready for service, whenever the need should arise. This includes 35x12.5x20 Toyo M/Ts for daily driver use, 35x12.50x17 Super Swamper STSs for the pulling track and 33x12.50x18 Toyo Proxess for the racetrack. Who knows what his other two sets are for.
In the cab Moon can monitor the truck's vitals through Autometer NV series boost, trans, fuel pressure and pyro gauges. He has also installed a very cool turbo rpm gauge from Garrett. He says on a fuel-only run, his custom GT42R spins at as much as 130,000 rpm and he's seen it over 160k on nitrous runs. Speaking of nitrous, a single stage NOS kit has been installed for drag strip and dyno use. A Labonte Stage 2 water/methanol kit was also installed to help keep egts in check.
As for stats on the truck, it's done a best of 12.0 at 113 mph on fuel only in the thin air of Salt Lake City at Rocky Mountain Raceway, 11.5 at 118 on nitrous with just a single .50 jet. The best dyno numbers to date came from the 2008 Weekend on the Edge event where the LB7 put down a very impressive 828 hp and 1212 tq uncorrected on Edge's Superflow dyno. Not bad, considering it's just a large single charger and was run in 1:1 direct drive. As his daily driver, this truck is definitely something to be proud of, especially when you see his past pulling seasons results. Moon finished in first place at all but one of the pulls he competed in on the local circuit. He also placed second at the DHRA Utah Nationals in both the Super Street and Pro-Mod classes. The truck is definitely a force to be reckoned with, whether Moon is on the pulling track, drag strip or even flying by you on the freeway with his 24-foot trailer in tow.
Moon drives this truck to and from work every day of the week, races it at the drag strip on Friday nights and pulls with it on Saturdays. We think this truck fits Diesel Tech's daily driven performer requirements as good as any we've seen yet.
While the factory LB7 engine is a pretty solid built platform, at the horsepower range Moon was shooting for, some minor adjustments were made to improve reliability and performance. The origional pistons were cut about 20 thousandths of an inch shorter, which results in a lower compressions ratio. Dropping the compression ratio does one thing mainly, and that is relieve some of the stress the motor would endure during long runs at a higher boost. Lowering the compression ratio just keeps the motor happier at the performance level Moon was shooting for. Moon also removed the inner lip of the piston that protrudes into the fuel bowl to improve piston durability. When the injectors pulse width is expanded, and fuel is actually being injected for longer periods of time, the fuel can actually act like a blow torch on that thin protruding lip, by machining the lip out, you remove the weakest portion of the piston top. Again, improving durability and reliability at the higher 600+ hp range.
The keyway that has been cut into the crankshaft is strictly for strength and durability issues. The factory crank uses a small dowel pin to locate the reluctor wheel, which in high horsepower applications has a tendency to shear off. Misalignment of the reluctor wheel can have pretty damaging effects on the engine and it's performance, so the keyway is cut and used in place of the dowel pin. It's just stronger.
The GT4202R charger Moon uses on his Duramax is capable of building a lot of boost, especially with the amount of fuel that is being injected. Tuning adjustments to increase horsepower output can raise cylinder pressures to an almost unimaginable figure. The SoCal Diesel billet injector hold-downs and mounting studs were installed to combat those higher cylinder pressures. With factory hold downs at this power output, the injector and injector cup could actually lift inside the head, sending that cylinder pressure into the heads themselves which would pressurize the cooling system causing some unwanted issues.
The GT4202R used on this motor build required a t-4 mounting flange and since the factory turbo has it's own mounting base and pedestal, something would have to be built to hold the new charger. Moon fabbed up his own pedestal using a t-4 flange that would allow the large Garrrett charger to bolt right into place of the factory unit.