1,000 Horsepower 2007 LBZ Duramax Street Truck

Collin Casstevens Aims For 1,000 Horsepower With His 2007 Duramax Street Truck

How many of us have bought a truck thinking, “I’ll just do exhaust and a chip?” How many of us have actually stopped there? Collin Casstevens from Middletown, Indiana, had the same idea when he bought his 2007 GMC Sierra 2500—until he caught the diesel performance bug and saw the possibilities. Working at one of diesel motorsport’s hubs at Fleece Performance Engineering at the time of the build, and now as a machinist for Neturen USA, the 21-year-old Casstevens well knew the potential inside his Duramax, and the idea of a 1,000hp street truck was too much temptation to pass up. With the help of several of the industry’s top shops and their best components, he set out to overhaul his daily driver into a road warrior.

After Casstevens initially did his exhaust work and a tune, he felt compelled to give the truck a little more. Once he had bolted on a stock-appearing Fleece Cheetah turbo, upgraded CP3, and new injectors, he realized he was going to have to bolster his stock Allison transmission to handle the power he was making with the upgraded Duramax.

The Duramax configuration can make it challenging to keep a tidy engine bay, but Casstevens did it right with powder-coated Illusion Blueberry accents and outstanding pipe and wiring work.

Jacob Richards at Fleece helped Casstevens tear into the transmission to install a SunCoast Diesel 6Pac kit with Raybestos clutches, Transgo Jr. shift kit, a SunCoast Diesel 1058 billet triple-disc torque converter, Fleece Performance AlliLocker, and Merchant Automotive’s Pump Rub upgrade and transfer case brace. With his newly rebuilt transmission, the truck seemed like a complete build—until Richards said, “You should be good to go now unless you want to build the motor.” All it took was that seed of an idea to get Casstevens’ mind churning, envisioning a 1,000-horsepower street beast.

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With the pulley powder-coated to match the engine accents, the second Fleece PowerFlo 750 10mm CP3 stands out as it does its job of providing a high volume of high-pressure fuel to the oversized Fleece injectors

Soon Casstevens was talking to Chase Fleece and LJ Benshoof and Greg Lossi from Freedom Racing Engines to get the process started building his block. Using a core LBZ block as a starting point, the team at FRE was set to machine and build the short block. With a 0.020-over engine bore, cylinder heads milled with a competition valve job, bronze valve guides, FPE max life PSI springs, Chromoly retainers and keepers, Trend Performance Stage 3 push rods, CP-Carrillo connecting rods, Mahle Motorsport pistons, keyed and polished crank, SoCal Diesel 3388 cam, ARP main bolts and head studs with Grade C head gaskets, and all-new Clevite internal bearings, this LBZ was ready to breathe fire.

The S480 atmospheric turbo feeds air directly into the secondary S366 to boost the intake charge further before it cycles through the Banks intercooler and finally into the LBZ’s intake manifolds.

Back at Fleece Performance, Casstevens and some of the guys in the shop helped pull some long nights assembling the engine and installing the new heart in the ’07’s engine bay. Casstevens and the Fleece team further tightened up the Duramax with an ATI SuperDamper, new oil pump, and oil cooler, PPE Power exhaust manifolds and up-pipes, ATS Diesel dual pump kit with twin Fleece PowerFlo 750 10mm CP3s, PureFlow AirDog 200 4G fuel system, Banks Power Intercooler, and a SunCoast billet flexplate. Then they bolted the engine in place with a set of Merchant Automotive engine mounts. Expelling the fumes from the beast of an engine is a 5-inch JAMO exhaust system with a 6-inch tip. But even the built engine and single S366 turbocharger weren’t enough to quench Casstevens’ thirst for more power.

Vital components to the high-powered engine are the smoothly fabricated JAMO 5-inch exhaust (part of which is seen here) and the PureFlow AirDog 200 4G fuel pump and filter system to get plenty of clean #2 up to the dual Fleece CP3s.

The next stop on the road to glory was Seth Wallace and Jake Bells of BOFA (Build Overhaul Fabricate Anything) Performance in Fairmount, Indiana, to custom build a compound turbo setup for his GMC. This would be BOFA’s first kit for the Duramax powerplant, but they didn’t back down from the challenge. After tooling and retooling their fabrication, the crew was able to craft a sleek and powerful compound setup, sporting the S366 turbo as well as an S480. Casstevens’ attention to detail shined as he made sure to dress up the upgraded engine components in an electric Illusion Blueberry powder coat finish by Shane Marshell at PCT Coatings tied in throughout the engine bay. With an expert tune by Brayden Fleece, this LBZ was set to top some charts.

With Fleece’s tie-rod sleeves and Bilstein 5100 shocks and steering stabilizer, the front end is equipped to hold steady when the potent LBZ is unleashed

Later, Casstevens upgraded his transmission further to keep up with the power with SunCoast billet input, output, and intermediate shafts, billet C2 and P2 hubs modified P1 sun gear, and swapped to a SunCoast 1053 torque converter for a higher rpm stall speed. With this configuration, Casstevens was able to put down an impressive 950 horsepower and 1,765 lb-ft of torque in his street-driving Duramax. And with some even more aggressive tunes loaded now, he plans to break that coveted 1,000-horsepower mark next time he straps the truck down to a dyno.

After removing the rear overload springs, Casstevens installed Caltrac traction bars to ensure the rear end would hook up under power.

With all that power coursing through the veins of the Sierra, Casstevens had to focus on getting it to the street and keeping it there. To counter a weak point often found in powerful GMs, Casstevens installed Fleece Performance tie-rod sleeves. Tightening up the performance truck’s ride are the two-inch Belltech drop shackles, Bilstein 5100 front shocks and steering stabilizer, Caltrac traction bars, and the removal of the rear overload springs. Hostile Havoc 20-inch wheels were selected and paired with 305/50 Nitto 420s for grip down the road.

The focus of the build had been to cram immense power into a streetable machine, so when it came to aesthetics, Casstevens opted for a subtle, sleeper exterior and comfortable interior. Spencer Baledge in Alexandria, Indiana, helped color-match the Silver Birch factory paint into the mirrors, handles, and bumper plastics for a sleek custom look. A billet aluminum grille with the GMC logo removed, aftermarket headlights, and tinting on all three brake lights added some subtle touches to catch your eye. Inside, the factory gray leather remains with the only visible modifications being the AutoMeter A-pillar gauge pod with Ultra-Lite II gauges and an Edge Products tuner overhead. Audible customization comes from a JL Audio 6W3 sub replacing the factory Bose model inside the center console and a JL Audio 200-watt amp tied into the sound system.

The overhead Edge tuner and AutoMeter pod with Ultra-Lite II gauges are the only giveaways of customization on the inside—until you hear some additional boom from the JL Audio 6W3 subwoofer in the center console powered by a JL Audio 200-watt amplifier.

All it took was that first upgrade and a little encouragement and Casstevens caught the performance bug. Even with a lofty goal, he was able to pull together his dream truck with help from friends at Fleece Performance Engineering, BOFA Performance, Freedom Racing Engines, and his brother Jarren Casstevens. Living up to the goal, Casstevens 2007 GMC Sierra 2500 rides like a daily driver—that is, until you mash the throttle and let the beast come to life. Continuing to prove it can take the street or the track, on a recent 200-mile trip with the nearly 1,000-horsepower machine, it averaged 19 mpg. Casstevens truly built an awesome diesel truck.

Inside is a familiar sight as Casstevens left the gray leather-clad interior alone to keep the roomy crew cab comfortable for road trips with friends and family.

Grippy Nitto 305/50R20 NT420S tires wrap around 20-inch Hostile Havoc wheels on all four corners to add some style as well as traction for the Sierra.

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What are some of the improvements the LBZ Duramax had over the LLY engine?

Key Improvements of the LBZ Duramax Over the LLY Engine

The LBZ Duramax came with a host of enhancements compared to its predecessor, the LLY. These improvements significantly increased both power and reliability. Here’s a breakdown of the notable upgrades:

Engine Block & Internal Components: One of the primary differences lies in the thicker engine block casting and the use of more robust connecting rods. These changes provided superior durability and power, outclassing earlier models.
Enhanced Main Bearing Strength: The main bearing regions of the LBZ were reinforced with additional webbing and taller bearing caps. The bores for the main cap bolts were also made 4mm deeper, allowing for increased structural integrity. To accommodate these deeper bolt holes, the oil feed holes were designed to be 2mm smaller.
Rods and Fuel System: The connecting rods maintained the dependable steel-forged, cracked-cap design found in prior versions but were made heftier at the big end. This adjustment enabled the rods to support about 100 additional horsepower. The LBZ also featured an improved high-pressure common-rail fuel system, along with new fuel rails and injectors, boosting horsepower and torque.
Turbocharger and Temperature Management: The turbo inlet manifold was enlarged, eliminating the compressor side bottleneck found in the LLY. This change led to reduced intake and exhaust temperatures, enhancing overall engine efficiency.

Each of these enhancements contributed to making the LBZ a more formidable and reliable engine compared to the LLY model.

What made the LBZ Duramax engine special compared to its predecessors?

What Set the LBZ Duramax Engine Apart?

The LBZ Duramax engine holds a unique place in automotive history, mainly due to its pairing with the robust six-speed Allison 1000 automatic transmission. This combination allowed it to handle more power effectively compared to its predecessors, which featured a five-speed transmission.

Key Features of the LBZ Engine:

Emission-Free Performance: The LBZ was the last of its kind without stringent emissions control systems, which means it avoided the fuel economy dip and longevity issues faced by later models.
Enhanced Durability: This generation saw significant upgrades, such as more intricate webbing in key areas of the engine, and reinforced main bearing caps with deeper bores for main cap bolts. These enhancements provided a solid foundation for improved horsepower and torque.
Sturdier Components: The connecting rods of the LBZ were designed with a beefier structure, particularly on the big end, enabling them to handle an additional 100 horsepower. Despite the increase in rotating mass, incidences of bent rods were rare, showcasing their reliability.
Advanced Fuel System: The engine benefited from upgraded fuel rails and injectors working in harmony with a higher-pressure common-rail system, thanks in part to the Bosch CP3 fuel pump. This configuration contributed significantly to its increased horsepower and torque.
Improved Turbocharger Design: A larger turbo inlet manifold eliminated previous bottlenecks in airflow, resulting in cooler intake and exhaust temperatures. This refinement also eased the turbocharger’s workload, reducing lag and enhancing overall efficiency.

In essence, the LBZ Duramax engine made notable strides in performance and durability, making it a highly sought-after choice among diesel enthusiasts—even more than a decade after production ceased.

How did the LBZ Duramax engine differ in terms of emissions technology from later models?

The LBZ Duramax engine stands out from its successors primarily due to its lack of emissions control technology, which sets it apart from later diesel models. Unlike the engines that followed, the LBZ wasn’t equipped with modern emissions systems designed to reduce pollutants. As a result, it managed to avoid some of the fuel economy drawbacks and potential shortening of engine lifespan associated with those systems.

This absence of emissions technology meant that the LBZ could deliver robust performance without the added complexities of components like diesel particulate filters (DPF) or selective catalytic reduction (SCR). Enthusiasts and drivers often seek out vehicles equipped with the LBZ because it offers a blend of power and longevity that became more challenging to find in later models weighed down by stringent emissions requirements.

In essence, the simplicity of the LBZ allows for fewer maintenance headaches, providing a more straightforward alternative to newer engine models that prioritize lowered emissions over raw performance.

How did the short-lived LBZ Duramax make its mark in the automotive industry?

The Legacy of the LBZ Duramax: A Powerhouse in Automotive History

The automotive world often sees engines come and go, but few have left an imprint as significant as the 6.6-liter Duramax LBZ. Though it was only produced for a brief stint, this engine carved out a niche thanks to its impressive performance and reliability.

Performance Upgrade

When it burst onto the scene, the LBZ was essentially a more finely tuned version of its predecessor, the LLY. What set it apart was its formidable increase in power, boasting an impressive 360 horsepower compared to the LLY’s 310. Torque also saw a significant bump from 605 pound-feet to a robust 650 pound-feet, making it a force to be reckoned with on the road.

Engine Enhancements

The LBZ wasn’t just about numbers on paper; it featured tangible mechanical improvements. It utilized a thicker engine block casting and sturdier connecting rods, which contributed to its enhanced durability. Plus, the addition of a higher pressure common-rail fuel system meant it could deliver both power and dependability like no other Duramax before it.

Impact Despite Short Production

Despite its short production run, the LBZ quickly became a favorite among enthusiasts and professionals alike. Its design avoided the complications of stringent emissions technology that were beginning to become standard, enhancing its appeal to those seeking simplicity without sacrificing performance.

In essence, the LBZ Duramax has become legendary not just for what it accomplished during its brief existence, but for setting a standard of excellence that continues to influence diesel engine design today.

What improvements were made to the LBZ Duramax’s fuel system and turbocharger?

Once he had bolted on a stock-appearing Fleece Cheetah turbo, upgraded CP3, and new injectors, he realized he was going to have to bolster his stock Allison transmission to handle the power he was making with the upgraded Duramax.

The LBZ Duramax had already set a strong foundation with its fuel system and turbocharger advancements. It featured new and improved fuel rails and injectors, augmenting a higher-pressure common-rail system that boosted horsepower and torque. The Bosch CP3 fuel pump was integral to generating the necessary pressure, making it a key player in the engine’s enhanced performance.

With the pulley powder-coated to match the engine accents, the second Fleece PowerFlo 750 10mm CP3 stands out as it does its job of providing a high volume of high-pressure fuel to the oversized Fleece injectors.

A larger turbo inlet manifold was employed in the LBZ, removing the previous bottleneck from the turbocharger’s compressor side. This resulted in cooler intake and exhaust temperatures, allowing the turbocharger to work more efficiently and with reduced lag—a feature that carried through to our custom setup.

Using a core LBZ block as a starting point, the team at FRE was set to machine and build the short block. With a 0.020-over engine bore, cylinder heads milled with a competition valve job, bronze valve guides, FPE max life PSI springs, Chromoly retainers and keepers, Trend Performance Stage 3 push rods, CP-Carrillo connecting rods, Mahle Motorsport pistons, keyed and polished crank, SoCal Diesel 3388 cam, ARP main bolts and head studs with Grade C head gaskets, and all-new Clevite internal bearings, this LBZ was ready to breathe fire.

The S480 atmospheric turbo feeds air directly into the secondary S366 to boost the intake charge further before it cycles through the Banks intercooler and finally into the LBZ’s intake manifolds.

Vital components to the high-powered engine are the smoothly fabricated JAMO 5-inch exhaust (part of which is seen here) and the PureFlow AirDog 200 4G fuel pump and filter system to get plenty of clean #2 up to the dual Fleece CP3s.

What were the performance characteristics of the LBZ Duramax engine?

The Duramax LBZ, a highly regarded engine among enthusiasts, was built for performance and reliability. Originally produced for just two model years, it was a more aggressively tuned version of the LLY. With a power output of 360 horsepower and 650 pound-feet of torque, the LBZ surpassed its predecessor, which had 310 horsepower and 605 pound-feet of torque. This engine employed a thicker block casting, meatier connecting rods, and a high-pressure common-rail fuel system, which collectively enhanced its power and dependability.

The Duramax configuration can make it challenging to keep a tidy engine bay, but Casstevens did it right with powder-coated Illusion Blueberry accents and outstanding pipe and wiring work.

Jacob Richards at Fleece helped Casstevens tear into the transmission to install a SunCoast Diesel 6Pac kit with Raybestos clutches, Transgo Jr. Shift kit, a SunCoast Diesel 1058 billet triple-disc torque converter, Fleece Performance AlliLocker, and Merchant Automotive’s Pump Rub upgrade and transfer case brace. With his newly rebuilt transmission, the truck seemed like a complete build—until Richards said, “You should be good to go now unless you want to build the motor.” All it took was that seed of an idea to get Casstevens’ mind churning, envisioning a 1,000-horsepower street beast.

The LBZ was designed without the burdens of strict emissions technology, a factor that contributes to its popularity. It featured a larger turbo inlet manifold, which eliminated previous airflow restrictions, allowing for cooler intake and exhaust temperatures and reducing turbo lag.

The S480 atmospheric turbo feeds air directly into the secondary S366 to boost the intake charge further before it cycles through the Banks intercooler and finally into the LBZ’s intake manifolds.

The next stop on the road to glory was Seth Wallace and Jake Bells of BOFA (Build Overhaul Fabricate Anything)Performance in Fairmount, Indiana, to custom build a compound turbo setup for his GMC. This would be BOFA’s first kit for the Duramax powerplant, but they didn’t back down from the challenge. After tooling and retooling their fabrication, the crew was able to craft a sleek and powerful compound setup, sporting the S366 turbo as well as an S480. Casstevens’ attention to detail shined as he made sure to dress up the upgraded engine components in an electric Illusion Blueberry powder coat finish by Shane Marshell at PCT Coatings tied in throughout the engine bay. With an expert tune by Brayden Fleece, this LBZ was set to top some charts.

With Fleece’s tie-rod sleeves and Bilstein 5100 shocks and steering stabilizer, the front end is equipped to hold steady when the potent LBZ is unleashed.

What enhancements were made to the turbocharger and airflow systems?

A larger turbo inlet manifold in the LBZ reduces bottlenecks, resulting in cooler intake and exhaust temperatures and less turbo lag.

What changes were made to the fuel system of the LBZ?

The LBZ includes a higher pressure fuel system with new fuel rails and injectors, contributing to its enhanced horsepower and torque.

What mechanical improvements were made to the LBZ engine?

The LBZ features a thicker engine block, more robust connecting rods, and an upgraded high-pressure common-rail fuel system to boost power and reliability.

How does the LBZ compare to its predecessor, the LLY, in terms of performance?

The LBZ surpasses the LLY by delivering an additional 50 horsepower and 45 lb-ft of torque, alongside several mechanical enhancements for improved performance.

What are the stock horsepower and torque ratings of the LBZ engine?

The stock LBZ engine produces 360 horsepower and 650 lb-ft of torque.

What are the detailed specifications of the LBZ Duramax engine?

Using a core LBZ block as a starting point, the team at FRE was set to machine and build the short block. But before diving into the enhancements, let’s explore the foundational specs that make up this powerhouse.

LBZ Duramax Engine Specifications

Production Years: 2006, 2007
Design: 90-degree V8
Bore: 4.06 inches
Stroke: 3.90 inches
Displacement: 6.6-liter (403 cubic inches)
Compression Ratio: 16:8:1
Block: Deep skirt, cast iron

Fuel & Emissions Systems

Injection System: Bosch high-pressure common-rail direct injection
Intercooler: Air to air
Emissions: Exhaust gas recirculation, diesel oxidation catalyst

Performance Metrics

Horsepower: 360 at 3,200 RPM
Torque: 650 pound-feet at 1,600 RPM

Valvetrain and Components

Valvetrain: OHV, four valves per cylinder, single cam
Rods: Forged steel, fractured cap
Pistons: Cast-aluminum
Heads: Cast aluminum with six 14mm diameter bolts per cylinder
Turbocharger: Garrett GT3788VA VVT
Injection Pump: Bosch CP3
Injectors: Bosch solenoid

With these robust specifications as a foundation, the FRE team elevated the LBZ to new heights. With a 0.020-over engine bore, cylinder heads milled with a competition valve job, bronze valve guides, FPE max life PSI springs, Chromoly retainers and keepers, Trend Performance Stage 3 push rods, CP-Carrillo connecting rods, Mahle Motorsport pistons, keyed and polished crank, SoCal Diesel 3388 cam, ARP main bolts and head studs with Grade C head gaskets, and all-new Clevite internal bearings, this LBZ was ready to breathe fire.

By marrying these initial specs with high-performance modifications, the LBZ engine not only maintained its legendary durability but also achieved unprecedented levels of power and efficiency.

What is the purpose of the billet main girdle, and how does it address engine durability at high power levels?

Reinforcing the Foundation: The Role of the Billet Main Girdle

To keep up with the monumental horsepower goals—and to counter the Duramax’s well-known tendency for main cap movement when pushed hard—Collin equipped his build with a billet main girdle. This component acts almost like a structural backbone for the lower end, tying all the main caps together and securing them to the pan rail. The result? It drastically reduces the chance of flex or distortion in the main caps, a weakness that can show up as uneven bearing wear when the power numbers climb into four digits.

Unlike running just ARP main studs and cross bolts (which are solid upgrades by themselves), the addition of the billet girdle provides much-needed lateral strength, limiting cap walk and keeping critical engine internals supported—even under the stress of big boost and big RPM. For those looking to combine it with an aftermarket high-capacity oil pan, just a heads up: clearances might get tight near the factory crossmember. Small trade-offs for peace of mind at 1,000+ horsepower.

Are there any potential fitment issues with aftermarket oil pans and the included main girdle?

Considering Aftermarket Oil Pans and Main Girdle Fitment

One point worth noting: if you’re running an aftermarket high-capacity oil pan—like those from PPE, Moroso, or similar brands—paired with the main girdle, you may run into clearance issues with the stock crossmember. The extra depth and revised design of larger oil pans can sometimes interfere, especially once you’ve added the beefier girdle for engine reinforcement.

Before final assembly, it’s wise to double-check how your chosen pan and the girdle fit together in your setup. Minor modifications or shimming might be required to get everything to clear, so a quick mock-up and close inspection can save a lot of headache down the road.

Are any covers or small parts excluded from the short block assembly and need to be transferred from the original engine?

Transferring Factory Covers and Small Components

While the FRE-built LBZ short block comes well-equipped with race-ready internals, you’ll need to bring over some essentials from your original engine. Certain factory covers and miscellaneous small parts aren’t included with the assembly—so plan on swapping these items over from your stock short block to complete the install. This extra step helps ensure a proper fit and keeps everything buttoned up just like GM intended.

What are the features and benefits of the billet steel flexplate included in the assembly?

Billet Steel Flexplate: Built for Strength and Performance

Nestled within the heart of this transmission overhaul is a billet steel flexplate—one serious upgrade over stock. This single-piece billet unit is not only more robust, but also manages to shave a bit of weight, further boosting efficiency where it counts. Meeting the demanding SFI 29.3 specification, it’s built to handle the relentless torque and high RPM punishment that comes with chasing four-figure horsepower.

Why does it matter? In short:

Superior Strength:Forged from a single slab of steel, the billet flexplate resists flex and cracking, even under extreme load.
Weight Advantage:Lighter than your average OE component, allowing the engine to rev more freely—and every bit counts on the street or strip.
Safety and Reliability:The SFI 29.3 certification means it’s tested for safety, so you can push your power goals with confidence.

It’s these small engineering details, tucked behind the scenes, that give builds like Casstevens’ the backbone needed to survive both daily driving duties and blasts down the quarter-mile.

What are the advantages of the included harmonic damper, and how does it improve engine performance?

The Benefits of an Upgraded Harmonic Damper

One key element that helps this Duramax thrive under pressure is the addition of the ATI Super Damper. This isn’t just a piece of flashy hardware—it’s a vital upgrade for any engine tasked with making serious power.

The ATI Super Damper works by controlling and minimizing harmful crankshaft vibrations, which are notorious for causing long-term damage, especially when horsepower numbers start to climb. By effectively absorbing and dissipating these crank harmonics, the damper offers three big benefits:

Enhanced Engine Longevity:By reducing vibration, the damper helps shield the crankshaft and other internal components from premature wear, giving your engine a longer, healthier life.
Improved Power Output:Less vibration translates into a smoother, more efficient engine. Many have seen a modest bump in available horsepower—sometimes up to a dozen extra ponies on the dyno—simply from changing out the stock unit.
Easy Monitoring and Maintenance:The ATI Super Damper bolts directly to the crank hub, keeping timing marks accurate. It’s rebuildable too, meaning that as the elastomer strips wear out and timing marks shift, they’re easy to service—no need to start from scratch.

When aiming for lofty power goals, small details like upgrading the harmonic damper can have a big impact on performance and long-term reliability. This level of attention to detail is what separates a temporary build from a powerhouse built to last.

What head gasket is recommended for use with this short block?

Head Gasket Selection

When it came to sealing up all that fresh horsepower potential, the team relied on a set of Grade C head gaskets to keep the combustion pressure where it belongs. These heavy-duty gaskets are a popular choice among LBZ builders looking for reliability under big boost, and they’re trusted to handle the kind of power numbers Collin was throwing down.

Are there optional upgrades available for the short block, and what are they?

Optional Upgrades for the Short Block

For those looking to elevate performance even further, several optional enhancements can be considered during the short block build. Among the most notable:

Fingers Oval Bowl pistonsfor added strength and longevity under extreme conditions
Performance short block kitsthat bundle various race-proven components for a tailored power package
Performance crankshaft gearoptions designed to handle elevated power levels with superior reliability
CP-Carrillo Pro-H 9321 connecting rods, renowned for their exceptional durability and track-proven pedigree

These upgrades allow owners to fine-tune their engine’s internals for high-boost applications, paving the way for more aggressive power goals—all while keeping peace of mind on the street or strip.

What type of engine applications is this short block intended for (e.g., power levels, turbo setups, towing)?

This robust build is a popular choice for enthusiasts pushing their engines with compound turbos, dual CP3s, or a fully built transmission—just like you’d expect in any serious 1,000hp street truck or heavy-duty tow rig. Even for those whose power goals are more modest, this kind of assembly brings peace of mind for anyone who isn’t afraid to put their engine through its paces, day after day.

The S480 atmospheric turbo feeds air directly into the secondary S366 to boost the intake charge further before it cycles through the Banks intercooler and finally into the LBZ’s intake manifolds.

What new internal components are included in the short block assembly?

A Bulletproof Foundation for Four Digits

Going deeper, the FRE short block build left no stone unturned in the quest for strength and reliability at 1,000+ horsepower. The rotating assembly started with a fully balanced and prepped crankshaft, which was not only keyed and polished but also designed to handle big power without breaking a sweat. The CP-Carrillo connecting rods brought plenty of headroom, thanks to their forged H-beam construction and ARP L19 fasteners, giving peace of mind at the top end. Mahle Motorsport pistons, machined from OE castings with cast iron ring inserts, offered the perfect blend of daily driver longevity and the ruggedness needed for high boost and big fuel.

A billet main girdle was added to reinforce the bottom end, linking the main caps together and fighting off any hint of cap walk at high power levels. ARP main studs (extended to accommodate the girdle) kept everything in check, while a tri-metal performance main bearing set and Mahle/Clevite connecting rod bearings ensured smooth, reliable rotation no matter how hard the pedal was mashed.

The upgrades didn’t stop there—an ATI SuperDamper was fitted to keep crank harmonics under control and free up a little extra horsepower, while a billet flexplate ensured the drivetrain could take the punishment. A high-flow performance oil pump, lower gasket kit, and all-new thrust washers rounded out the internal upgrades, making this LBZ as stout as they come for street or strip.

With the foundation set, it was time to turn attention to airflow and fueling to match the short block’s potential.

What are the ratings and design features of the included performance pistons?

Built for Power and Longevity

A big part of the bottom end’s strength comes from the Mahle Motorsports Performance Cast Piston Kit—rated for up to 1,000hp and designed for all-around trucks making anywhere from 400 to 1,000 horsepower. These pistons are machined from OE castings and retain the cast iron ring insert, which means you get the driveability and longevity of an OEM replacement piston, but with the extra muscle needed for a built engine. Unlike some high-horsepower forged pistons that might need replacement after just 20,000 to 30,000 miles, these Mahle pistons are engineered to deliver over 100,000 miles in a high-output application. That makes them an ideal choice for a street-driven truck that’s expected to survive daily abuse and still put down four-digit power numbers without breaking a sweat.

What are the specifications and features of the included connecting rods?

Forged Strength Where It Matters Most

To ensure the bottom end could handle four-digit power, the build featured a set of Callies Compstar XtremeConnecting Rods (Part# CST6418MS0LCAX). These 4340 forged H-beam rods, conservatively rated at 1,000 horsepower and equipped with ARP L19 fasteners, provided exceptional durability and confidence for pushing the limits. This critical upgrade—paired with the Mahle pistons and polished, keyed crank—meant the short block was as robust as they come, prepped for both street reliability and race-track abuse.

What are the specifications and benefits of the included crankshaft?

Callies DuraStar Crankshaft: Strength for Serious Power

A crucial foundation for handling four-digit horsepower, FRE equipped the build with a Callies DuraStar crankshaft (Part# D333M81-CS), rated up to 1200hp. The DuraStar goes beyond the strength of the OEM GM Duramax crank, thanks to a substantially stronger steel alloy, a deeper nitride layer for durability, and unique machining features that ensure the rotating assembly can withstand the high stresses of a high-performance diesel engine. This crank was not just keyed and polished, but specifically chosen for its reputation in serious Duramax builds, guaranteeing reliability where lesser cranks might falter.

With every component hand-picked and machined for maximum reliability and performance, this wasn’t just a rebuild—it was an all-out effort to transform the LBZ into a true street beast, ready for anything Casstevens could throw at it.

What type of oil pump is included in the short block?

Casstevens and the Fleece team further tightened up the Duramax with an ATI SuperDamper, new oil pump—including a high-flow Dmax Performance Oil Pump—and oil cooler, PPE Power exhaust manifolds and up-pipes, ATS Diesel dual pump kit with twin Fleece PowerFlo 750 10mm CP3s, PureFlow AirDog 200 4G fuel system, Banks Power Intercooler, and a SunCoast billet flexplate.

Then they bolted the engine in place with a set of Merchant Automotive engine mounts. Expelling the fumes from the beast of an engine is a 5-inch JAMO exhaust system with a 6-inch tip. But even the built engine and single S366 turbocharger weren’t enough to quench Casstevens’ thirst for more power.

What bearing sets and thrust washer sets are included in the assembly?

With a 0.020-over engine bore, cylinder heads milled with a competition valve job, bronze valve guides, FPE max life PSI springs, Chromoly retainers and keepers, Trend Performance Stage 3 push rods, CP-Carrillo connecting rods, Mahle Motorsport pistons, keyed and polished crank, SoCal Diesel 3388 cam, ARP main bolts and head studs with Grade C head gaskets, and all-new Clevite internal bearings, this LBZ was ready to breathe fire.

To ensure the bottom end could handle the punishment of four-digit power, the build included a Mahle/CleviteConnecting Rod Bearing Set, Tri-Metal Performance Main Bearing Set, and a Mahle/Clevite Thrust Washer Set—all carefully selected for their durability under extreme load. Every component was chosen with reliability in mind, marrying race-inspired performance with the peace of mind only top-tier internals can bring.