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It’s been 10 years since GM stopped producing the LB7 Duramax, but thanks to their longevity, efficiency and performance potential, the 2001-2004 GM trucks are still some of the most sought after light duty diesels on the road today. It may be getting hard to come across super clean low mileage LB7 trucks, but even at higher mileage (150,000+) if an owner has been diligent with regular maintenance, the LB7 can make for a great daily driver. With nothing more than a basic intake and exhaust upgrade, fuel lift pump and some custom programming, the LB7 can produce around 530 rear-wheel horsepower. At these levels, owners will need to expect some transmission upgrades to support all that power, as the stock Allison 1000 in the 2001-2004 trucks will only hold around 430 hp safely before fifth gear clutch and torque converter slippage become an issue.

600 RWHP

With these modifications taken care of, the real performance-limiting factor with the LB7 Duramax is the factory IHI turbocharger. While the stock turbocharger can support up to 530 horsepower relatively safely, EGTs can get quite hot, and the stock compressor wheel will start pushing past its efficiency range. To overcome some of these issues, Duramax Tuner out of Marengo, Illinois, developed their Stealth 64 as a true drop-in replacement for the factory IHI turbocharger. After doing extensive in-house testing on both their Superflow chassis dyno and undergoing real world daily driving and towing situations, their new 64mm modified stock turbo offered gains of over 80 horsepower making 600+rwhp while maintaining that same responsive off-idle boost and fast spool-up owners become accustomed to from their stock turbos.

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 With nothing more than basic upgrades, the LB7 can produce around 530 rear-wheel horsepower.

HOW IT’S DONE

Built from take-off core turbochargers, Duramax Tuner tears the stock units completely down and reconditions them to virtually brand new conditions with an extensive and strict remanufacturing process that replaces all worn internals with new journal bearings, thrust bearing, seals and hardware. The factory turbine housings are inspected for cracks and are cleaned up to eliminate any rust or corrosion, and the factory wastegate actuator is modified to ensure maximum performance at higher boost levels. On the compressor side of things, the factory 10-blade compressor wheel is tossed in the recycle bin, and a larger extended tip 64mm compressor wheel replaces it inside a machined OEM compressor cover. The new compressor wheel design not only offers better airflow and increased volume but will keep pumping air efficiently up to 35-psi boost making for a much wider and more usable power curve. The rotating assembly is balanced on a high-speed balancer to ensure longevity under extreme conditions and higher shaft speeds.

1. The Stealth 64 from Duramax Tuner offers true drop-in, bolt-for-bolt installation for the 2001-2004 LB7 Duramax and will support over 600 hp while maintaining great daily driver and towing performance. The larger than stock 64mm compressor wheel inside the factory compressor cover offers phenomenal power and torque curves while keeping that stealth look under the hood—keeping the competition completely in the dark.

1. The Stealth 64 from Duramax Tuner offers true drop-in, bolt-for-bolt installation for the 2001-2004 LB7 Duramax and will support over 600 hp while maintaining great daily driver and towing performance. The larger than stock 64mm compressor wheel inside the factory compressor cover offers phenomenal power and torque curves while keeping that stealth look under the hood—keeping the competition completely in the dark.

DIRECT SWAP

The Stealth 64 offers a great performance upgrade without breaking the bank for those needing impeccable drivability on any truck from stock to 600 hp. Because the external pieces go unchanged, it’s an easy install with no other changes or kit pieces required to make a fit. Duramax Tuner does recommend, however, that the stock downpipe be replaced with a less restrictive 3-inch pipe, along with a high flow intake elbow to ensure that the larger compressor wheel can get all the air it needs. The Stealth 64 is a very versatile turbocharger that can be used as a stock replacement on a 400-hp truck used for heavy towing or daily driving. The 64mm compressor offers good low rpm torque and good airflow through the rpm range for maximum EGT control on long grades. For the hot street and performance-oriented crowd wanting to compete in Work Stock sled pulling classes around the country, the Stealth has supported 610 to 625 horsepower with proper fueling and tuning support.

Duramax Tuner

With the monstrous success of the Stealth 64 for the LB7 market, the Duramax Tuner crew has spent countless hours testing and developing an all new turbocharger to appease the 600-to-800-hp crowd, while maintaining that same factory drop-in style installation. Based off the durable Borg Warner S400 center section, Duramax Tuner’s all new Stealth 67 will use a custom cast compressor cover with the 2004.5-2010 Duramax VGT v-band style inlet to allow easier fitment for all model year Duramax trucks. On the exhaust side, they’ve taken things to an all new level of performance and ease of fitment by creating, casting and machining an all-new turbine housing from scratch. The all new turbine housing will allow the installation of the S400 style turbocharger without the need for an aftermarket pedestal, downpipe and charge air piping system. Using the same LB7 style downpipe flange, the internally gated housing will make for an easy install with great low-end response and the ultimate top end performance capable of supporting up to 800 hp. The Stealth 67 will also make a great base for a large compound kit that could support 1,100+hp depending on the fueling and larger atmospheric turbocharger. The all new Stealth 67 has been tested on the street and dyno with quite a few sled pulls and drag strip passes under its belt as well. With a schedule market release for fall of 2015, keep an eye on Duramax Tuner.com and the company’s social media pages for further information.

For those looking for more from their LB7 Duramax, the Stealth 64 may just fit fill that void, with solid power improvements and dyno charts to prove it. Whether your truck is used for towing a camp trailer on the weekends or yanking a sled down the dirt track at the local fair, the modified stock turbocharger can offer the airflow improvements needed to justify upgrading the old worn out turbo under the hood. DW

2. Built off of factory IHI turbocharger cores from the LB7 application, the used turbochargers are completely torn down, cleaned, bead blasted, machined, balanced and reconditioned to almost-new quality. All worn items are replaced, and some pieces are upgraded and modified to offer the best balance of power and drivability from a “stock appearing” turbocharger.

2. Built off of factory IHI turbocharger cores from the LB7 application, the used turbochargers are completely torn down, cleaned, bead blasted, machined, balanced and reconditioned to almost-new quality. All worn items are replaced, and some pieces are upgraded and modified to offer the best balance of power and drivability from a “stock appearing” turbocharger.

3. The original 60mm 10-blade compressor wheel that comes in the stock LB7 turbocharger is sufficient in a stock application and will support up to 530 rwhp with the right supporting mods, but its design really limits flow as engine RPMs increase. This creates a very ‘peaky’ power curve with power peaking around 2,700 rpm, at which point, power will start dropping drastically. This particular compressor wheel shows signs of poor air filtration and dusting that has damaged the front edges of the blades, which also hurts performance.

3. The original 60mm 10-blade compressor wheel that comes in the stock LB7 turbocharger is sufficient in a stock application and will support up to 530 rwhp with the right supporting mods, but its design really limits flow as engine RPMs increase. This creates a very ‘peaky’ power curve with power peaking around 2,700 rpm, at which point, power will start dropping drastically. This particular compressor wheel shows signs of poor air filtration and dusting that has damaged the front edges of the blades, which also hurts performance.

4. The new 64mm compressor wheels and turbine wheels are balanced as a complete rotating assembly on a high speed Heins Balancing Machine to ensure the new Stealth can offer the same durability and reliability you’d expect from an OEM turbocharger. With shaft speeds running in the 150,000+ RPM range, the slightest imbalance can really hurt longevity of the entire rotating assembly, including the wheels, bearings, shaft, and thrust washer.

4. The new 64mm compressor wheels and turbine wheels are balanced as a complete rotating assembly on a high speed Heins Balancing Machine to ensure the new Stealth can offer the same durability and reliability you’d expect from an OEM turbocharger. With shaft speeds running in the 150,000+ RPM range, the slightest imbalance can really hurt longevity of the entire rotating assembly, including the wheels, bearings, shaft, and thrust washer.

5. After some machining is completed on the compressor side back plate and the rotating assembly has been balanced, the center section can be assembled with all new internals that include new bearings, piston rings, snap rings and seals. The shaft and wheel are then torqued to spec.

5. After some machining is completed on the compressor side back plate and the rotating assembly has been balanced, the center section can be assembled with all new internals that include new bearings, piston rings, snap rings and seals. The shaft and wheel are then torqued to spec.

6. The assembled cartridge is now ready to be placed into the OEM turbine housing and freshly machined compressor cover. By keeping the same external pieces, the Stealth 64 can be installed into the truck with no other changes needed. However, to optimize performance, Duramax Tuner does recommend that a high flow 3-inch intake elbow and downpipe be used in place of the factory pieces.

6. The assembled cartridge is now ready to be placed into the OEM turbine housing and freshly machined compressor cover. By keeping the same external pieces, the Stealth 64 can be installed into the truck with no other changes needed. However, to optimize performance, Duramax Tuner does recommend that a high flow 3-inch intake elbow and downpipe be used in place of the factory pieces.

Duramax Tuner

7/8. The factory IHI turbocharger uses an internal wastegate to control exhaust flow and keep boost and exhaust back pressure in-check. Taking full advantage of this design, the Stealth 64 has had some minor changes made to the wastegate system to allow better performance in a high horsepower application. While the turbo is shipped with the actuator pre-set for optimum boost levels as a single turbo, the adjustable end link does make the Stealth 64 a great option as a high pressure unit in a compound turbo system.

7/8. The factory IHI turbocharger uses an internal wastegate to control exhaust flow and keep boost and exhaust back pressure in-check. Taking full advantage of this design, the Stealth 64 has had some minor changes made to the wastegate system to allow better performance in a high horsepower application. While the turbo is shipped with the actuator pre-set for optimum boost levels as a single turbo, the adjustable end link does make the Stealth 64 a great option as a high pressure unit in a compound turbo system.

9. While doing a turbocharger swap on LB7 trucks isn’t a job for the faint of heart, due to its design being based off the stock turbo, the Stealth will drop right in place of the stock unit. Depending on the condition of the truck, this job can take anywhere from 4 to 8 hours. The exhaust downpipe and manifold up-pipe bolts that thread into the back of the turbine housing can be a bit stubborn and will take some patience to break loose and remove.

9. While doing a turbocharger swap on LB7 trucks isn’t a job for the faint of heart, due to its design being based off the stock turbo, the Stealth will drop right in place of the stock unit. Depending on the condition of the truck, this job can take anywhere from 4 to 8 hours. The exhaust downpipe and manifold up-pipe bolts that thread into the back of the turbine housing can be a bit stubborn and will take some patience to break loose and remove.

10. Once dropped into place, the Stealth 64 looks right at home in the engine valley and, to an untrained eye, it looks completely stock— especially once the intake system is bolted back on. The new compressor wheel offers a broad power and torque curve with a more pronounced whistle under the hood.

10. Once dropped into place, the Stealth 64 looks right at home in the engine valley and, to an untrained eye, it looks completely stock— especially once the intake system is bolted back on. The new compressor wheel offers a broad power and torque curve with a more pronounced whistle under the hood.

11. The in-house chassis dyno at Duramax Tuner was extremely useful when testing and developing the Stealth line of turbochargers. The final production unit has proven to support gains of over 80 hp above the stock turbocharger while helping to reduce EGTs and improve towing performance with a much flatter power curve. This particular dyno chart comes from a 2001 truck with a set of 30% injectors, healthy stock CP3, DT750 built Allison transmission, DT ECM/TCM tuning, high flow intake elbow, 3-inch downpipe and low pressure fuel lift pump. With no changes to the tuning at all, horsepower jumped from the stock turbos impressive 530 hp to almost 609 hp.

11. The in-house chassis dyno at Duramax Tuner was extremely useful when testing and developing the Stealth line of turbochargers. The final production unit has proven to support gains of over 80 hp above the stock turbocharger while helping to reduce EGTs and improve towing performance with a much flatter power curve. This particular dyno chart comes from a 2001 truck with a set of 30% injectors, healthy stock CP3, DT750 built Allison transmission, DT ECM/TCM tuning, high flow intake elbow, 3-inch downpipe and low pressure fuel lift pump. With no changes to the tuning at all, horsepower jumped from the stock turbos impressive 530 hp to almost 609 hp.

Duramax Tuner

12/13. Nick Priegnitz, the owner of Duramax Tuner, just completed this immaculate frame-off restoration of his 1958 Chevrolet Apache truck. Running an LB7 Duramax and ZF-6 manual transmission, the truck will see its fair share of sled pulling action running around the local circuit in the Work Stock class with the Stealth 64 under the hood.

12/13. Nick Priegnitz, the owner of Duramax Tuner, just completed this immaculate frame-off restoration of his 1958 Chevrolet Apache truck. Running an LB7 Duramax and ZF-6 manual transmission, the truck will see its fair share of sled pulling action running around the local circuit in the Work Stock class with the Stealth 64 under the hood.

SOURCES:

Calibrated Power Solutions

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