Alternate Firing Camshaft: Strengthening A Duramax

With nearly 15 years of production, the 6.6L Duramax V-8 found in GM trucks has proven itself to be a durable and dependable diesel. Throughout its lifespan, the Duramax has gone through several revisions to improve performance and drivability as well as reduce emissions. Internal changes to the latest Duramax, the 2011-2015 LML, include new connecting rods, pistons, additional emissions equipment and a variable-geometry turbocharger, all of which have raised output to nearly 400 hp. One piece that has remained virtually unchanged, however, is the Alternate Firing Camshaft, which can fail prematurely when subjected to undue stress, especially in a high-performance or competition application.

The aftermarket has done some incredible things with the 6.6L Duramax, pushing it to performance levels that were never imaginable. It’s not uncommon to see all-out drag racing and sled pulling trucks with engines producing 1,500 hp or more. Getting that kind of power is no easy task: Shops specializing in Duramax performance have had to get quite technical and come up with some rather ingenious products to make a motor live at those levels. One such company is Empire Diesel of Dubuque, Iowa. Empire Diesel quickly gained popularity on the competitive sled pull scene in the Midwest thanks to their custom-built engines and overall knowledge of the Duramax platform. With their sled trucks pushing 1,000 horsepower, they too ran into the limitations of the stock crankshaft.

Empire determined that the factory firing order of the Duramax engine could be causing major stress along the crankshaft plane. By creating a new camshaft profile that changes the firing order, they thought it would be possible to distribute the stress of combustion more evenly across the crank. We interviewed Chad Remakel, CEO of Empire Diesel, to learn more about the Alternate Firing Order camshaft, and our conversation revealed some very interesting technical knowledge about the inner workings of the Duramax diesel and what it takes to really push these things to the limit.

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DIESEL WORLD: What’s the reasoning behind the Alternate Firing Camshaft order for the 6.6L Duramax?

CHAD REMAKEL: The main reason for modifying the Duramax firing order with the camshaft is to relieve stress on the front portion of the crankshaft in higher performance applications. The factory firing is 1-2-7-8-4-5-6-3, but this new camshaft design changes that to 1-5-6-3-4-2-7-8. Changing an engine’s firing order isn’t a new science, as GM gas guys have been doing it for years in with the LS engine 4-7 swap. It’s just something we wanted to try and help reduce part breakage in the Duramax application. Every engine platform within the Duramax family—including the LB7, LLY, LBZ, LMM and LML—suffers from these issues with the crankshaft breaking just behind the snout back to the #3 rod journal. We’ve seen these failures on everything from mildly modified daily drivers to full-blown competition engines with internally balanced aftermarket billet cranks. There is just something to do with the Duramax engines harmonics at higher rpm and bigger power levels that causes a lot of stress on the crank due to the factory firing order.

This illustration shows the difference between the factory GM firing order (bottom) and the new firing order of the Alternated Firing Camshaft developed by Empire Diesel. The GM Duramax has had troubles with crankshaft failures in high-horsepower applications, with the snout breaking off due to extreme stress load. The altered firing order helps to more evenly distribute those stresses across the entire length of the crankshaft, improving engine harmonics and durability. — 1. This illustration shows the difference between the factory GM firing order (bottom) and the new firing order of the Alternate Firing Camshaft developed by Empire Diesel. The GM Duramax has had troubles with crankshaft failures in high-horsepower applications, with the snout breaking off due to extreme stress load. The altered firing order helps to more evenly distribute those stresses across the entire length of the crankshaft, improving engine harmonics and durability.

2. Unfortunately, in the Duramax application, swapping out the camshaft isn’t an easy Saturday job, as the entire engine needs to be torn down to make the change properly. In most cases, making a camshaft swap would be recommended only when doing other internal engine work. Because of this, most camshafts are installed with multiple other changes like billet connecting rods, performance pistons, and cylinder head modifications, so it’s hard to get true back-to-back comparisons on a simple “cam swap.”

DW: When did Empire Diesel start to notice these problems and try to resolve them with this new camshaft design?

CR: In 2009 we continued to see Duramax crankshaft failures at around the 1000-horsepower mark. It seemed to be a roadblock we had to get around to push performance any further. We all sat down together to brainstorm, trying to come up with a simple and cost-effective way to make broken crankshafts a thing of the past. Looking at similar engine failures in our early performance gas engine background, these issues were more than likely related to harmonics and stress within the engine. There are only two legitimate ways to overcome that. One is to back down the power output, and the other is try to more evenly disperse that current stress across the crankshaft.

3. After lubing the camshaft with the correct break in oil, it must be slid into the engine block using extreme care. The smallest ding or nick in one of the cam journals or lifter lobes can cause serious engine problems that could lead to poor engine performance and even a catastrophic failure.

4. Once installed in the engine block, the camshaft has a small two-bolt retainer that holds it in place. All performance camshafts offered by Empire Diesel come pre-machined with a keyway on the end to help with locating the timing gear set. The keyway is a much stronger design than the factory dowel pin, which has been known to shear off in higher-performance applications.

5. When installing a camshaft it’s vital that it be “degreed” using a degree wheel to check that the camshafts lobes will open each cylinder's intake/exhaust valves at the proper moment. The camshaft comes with a “cam card” that tells the engine builder exactly what the cam's specifications are and at what degree the camshaft should be set at in correlation to the #1 piston's top dead center position. — 5. When installing a camshaft it’s vital that it be “degreed” using a degree wheel to check that the camshafts lobes will open each cylinder’s intake/exhaust valves at the proper moment. The camshaft comes with a “cam card” that tells the engine builder exactly what the cam’s specifications are and at what degree the camshaft should be set at in correlation to the #1 piston’s top dead center position.

6. Using a strap plate, Empire Diesel technicians check for true top dead center (TDC) of the #1 piston before going further with the cam installation and degreeing process. A reputable engine builder may have another method of checking this, but getting the camshaft set perfectly will ensure that maximum valve lift and duration is held without damaging pistons or cylinder heads due to incorrect clearance.

DW: When it came time to actually change the firing order, how did you determine the order for the injection events?

CR: Looking at our options for firing order really just took a pencil, paper and some pretty terrible drawing skills. We basically just had to connect the dots to see which pattern would distribute the stresses of each cylinder’s combustion event on the crankshaft most efficiently.

7/8. Using a small wire attached to the engine block, once true TDC is found, the timing wheel can be set at zero according to the pointer. The engine builder then rotates the engine clockwise until the #1 piston again reaches TDC. A mark is then made on the degree wheel where the pointer shows its current location. The crankshaft should then be turned clockwise until #1 TDC is reached again. If the degree wheel was setup properly, the first recorded timing mark and the second should be equal.

DW: Once the firing order was determined, was it just as simple as making a new camshaft and replacing the stock cam?

CR: In theory, yes, but it wasn’t quite that easy. Back then the major performance camshaft manufacturers were only up to speed with gasoline engines and wanted nothing to do with diesels. It was a pretty long, drawn-out struggle getting somebody to produce exactly what we were needing for what they referred to as a ‘limited market’ at a reasonable price. After months of calling and tons of legwork we finally had the first alternate fire order Duramax camshaft in our hands. This wasn’t the end, however, as we still needed to figure out how to get the ECM [engine control module] to recognize the change in camshaft profile. After some investigation we discovered all the ECM needed to initiate the firing order of the injectors was to see the trigger on the tone wheel. This trigger tells the ECM when it needs to fire the #1 cylinder injector, after that, the ECM doesn’t care in what order the remaining seven injectors fire. So if an injector signal was moved from its original intended firing location, as long as the moved injector signal matched the opening or closing strokes of valves in that particular cylinder the engine would run like factory.

DW: So what electronic changes are required to adjust the injector firing order when making this camshaft change?

CR: There are two ways to go about the electronics for this. One would be moving and extending your factory injector wiring harnesses and the other would be moving pin locations on the injection harness itself. We’ve heard that EFILive is currently working on new tables that will allow firing order changes to be done within their custom tuning software. However, even if this does become an option, while it would be easier, we’d still suggest making the change by doing the pin swap as there would be less risk of causing engine problems from the possibility of loading the wrong tune.

9/10. The timing marks on both the crankshaft and camshaft need to align with each other as well; this ensures the lifter and valve movement happens as it should. Depending on where the camshaft's keyway has been machined, these timing marks may be off by up to four degrees, so Empire Diesel offers a modified camshaft gear and four offset keyways to get the camshaft degree perfect when setting up the motor. — 9/10. The timing marks on both the crankshaft and camshaft need to align with each other as well; this ensures the lifter and valve movement happens as it should. Depending on where the camshaft’s keyway has been machined, these timing marks may be off by up to four degrees, so Empire Diesel offers a modified camshaft gear and four offset keyways to get the camshaft degree perfect when setting up the motor.

DW: After running this Alternate Fire Camshaft and selling to so many customers through the years since its inception, has your initial camshaft profile stayed the same or do you continue to try new things to improve performance and reliability?

CR: Over the past five years we have had great success with this process and helping to keep the Duramax crankshafts and engines alive. Some customers think this alternate firing order also better distributes air through the intake manifold for better combustion, but we haven’t been able to verify this. Since that early testing our camshaft profiles have become more aggressive and we now offer a Street or Competition version, along with being able to build a custom profile to fit a customer’s specific requirements. This past 2014 sled pulling season was very successful for us and our customers running our camshaft designs. While we would love to give specific examples of each of our customer’s accomplishments, many are competing against each other and we need to keep some of that information to ourselves. We have recently teamed up with Wagler Competition Products and have seen extremely impressive results when our cam profiles are paired with Jeremy Wagler’s Duramax cylinder head program.

11. Once the degree wheel and pointer location have been checked, a lifter and pushrod can be dropped down into the #1 cylinder and a dial indicator setup to measure lifter travel. By rotating the engine a few times, the cam degree process will start when the lifter is on the “heel” or the cam base circle, which is the lowest point in its travel. The dial indicator should then be zeroed here.

DW: What kind of performance gains can be expected from making this camshaft change?

CR: In our early engine dyno testing in 2009-2010 we immediately noticed a much smoother idle along with a noticeable difference in engine tone at higher rpm. To date, the biggest horsepower we’ve seen from this camshaft over a stock cam is about 28 hp on the engine dyno. But this wasn’t developed with more horsepower in mind. We were really looking to improve durability at higher horsepower levels, which this technology has done. While this Alternate Fire technology has made major improvements when it comes to durability and pushing the horsepower limits of the Duramax platform, nothing is ever a sure thing. This camshaft design is not the “golden ticket” to guarantee your engine won’t fail, as your choice of other parts, assembly and tuning is just as vital. There are a few other little tricks we do to the engines we build in-house, but we can’t give away all our secrets.

12. The engine's crankshaft is then rotated clockwise one last time until the dial indicator reads 0.050. The reading seen on the degree wheel at the pointer at this location is the lift on the camshaft with the intake lobe opening. You can now compare this reading to what is found on the cam card supplied with the camshaft. If the numbers match, the camshaft is set correctly and you can move on with the build. If the numbers are not the same, an offset timing key or changes with the timing gear will need to be made. Factory specs allow for a +/-1 degree tolerance due to gear lash and wear on the teeth. — 12. The engine’s crankshaft is then rotated clockwise one last time until the dial indicator reads 0.050. The reading seen on the degree wheel at the pointer at this location is the lift on the camshaft with the intake lobe opening. You can now compare this reading to what is found on the cam card supplied with the camshaft. If the numbers match, the camshaft is set correctly and you can move on with the build. If the numbers are not the same, an offset timing key or changes with the timing gear will need to be made. Factory specs allow for a +/-1 degree tolerance due to gear lash and wear on the teeth.

DW: Are the alternate fire camshafts only required in full competition builds?

CR: We actually recommend making this conversion in any engine build from a mild towing and street application to our all-out 1,500-hp+ competition builds. We’ve seen completely bone-stock trucks come through our shop with broken crank snouts so we offer our Alternate Fire Camshaft in multiple profiles to suit each application. Our mild Street grind works in an otherwise stock motor with stock pistons, no valve reliefs required. These can help with the power and torque curve making the truck better to daily drive and tow with. Our more performance-oriented grinds get much more aggressive and require other engine modifications to work properly. We also offer the camshaft as a “blank” so it can be purchased and sent to your preferred engine builder or machine shop to accept the profile they prefer. DW

SOURCE:

Empire Diesel

563.588.2708

FREQUENTLY ASKED QUESTIONS

How does the condition of the crankshaft affect the outcome of using an alternate-firing camshaft?

The condition of the crankshaft plays a crucial role when using an alternate-firing camshaft. A used crankshaft may have already endured considerable stress from conventional firing orders. Introducing a different firing pattern can exert new stresses, potentially increasing the crankshaft’s risk of failure.

In contrast, a new crankshaft—even if it’s a standard model—can significantly improve engine harmonics when paired with an alternate-firing camshaft. However, reports indicate that some new stock crankshafts still face breakage. This suggests variability in how they handle the stresses introduced by alternate firing orders.

For those seeking to reduce risk, opting for a billet crankshaft with narrow-rod design could be advantageous. These crankshafts enhance durability by fortifying the fillet radius, thereby providing greater resilience against failure when subjected to the stresses of an alternate-firing camshaft.

What role do major crankshaft companies play in developing alternate-fire camshafts?

Major crankshaft companies are at the forefront of innovating alternate-fire camshafts, which are essential for enhancing the performance of engines like the Duramax. These companies research and design camshafts that improve engine efficiency and power output. By offering products that cater to different performance levels, they allow engine builders to customize engines for specific needs.

In their role, these companies collaborate closely with engine builders and technical experts to ensure the correct camshaft selection for various applications. This process involves detailed consultation, where experts assess the unique requirements of a project to recommend the best camshaft configuration.

Through their expertise and advanced engineering capabilities, crankshaft companies not only produce high-quality components but also provide invaluable guidance to ensure these camshafts are effectively integrated into engine systems. This helps maximize performance while maintaining reliability.

Can alternate-firing camshafts completely prevent Duramax crankshaft failures?

DW: What kind of performance gains can be expected from making this camshaft change?

CR: In our early engine dyno testing in 2009-2010, we immediately noticed a much smoother idle along with a noticeable difference in engine tone at higher RPM. To date, the biggest horsepower gain we’ve seen from this camshaft over a stock cam is about 28 hp on the engine dyno.

But this wasn’t developed with more horsepower in mind. We were really looking to improve durability at higher horsepower levels, which this technology has done. While this Alternate Fire technology has made major improvements when it comes to durability and pushing the horsepower limits of the Duramax platform, nothing is ever a sure thing.

These camshafts help reduce harmonics and extend bearing life, which are crucial for engine longevity. However, they are not the complete solution for preventing crankshaft failures. There have been cases of broken crankshafts even with these cams installed. This design isn’t the “golden ticket” to guarantee your engine won’t fail, as your choice of other parts, assembly, and tuning is just as vital.

There are a few other little tricks we do to the engines we build in-house, but we can’t give away all our secrets.

Have there been instances of crankshaft failures even with alternate-firing camshafts installed?

Yes, there have been instances of crankshaft failures even when these camshafts are used.

What specific benefits do alternate-firing camshafts provide?

They help in reducing engine harmonics and extending the life of bearings.

Can alternate-firing camshafts completely prevent crankshaft failures?

No, alternate-firing camshafts are not a complete solution to prevent crankshaft failures.

What is an alternate-firing Duramax cam?

CHAD REMAKEL: The main reason for modifying the Duramax firing order with the camshaft is to relieve stress on the front portion of the crankshaft in higher performance applications. The factory firing is 1-2-7-8-4-5-6-3, but this new camshaft design changes that to 1-5-6-3-4-2-7-8. Changing an engine’s firing order isn’t a new science, as GM gas guys have been doing it for years with the LS engine 4-7 swap. It’s just something we wanted to try and help reduce part breakage in the Duramax application. Every engine platform within the Duramax family—including the LB7, LLY, LBZ, LMM, and LML—suffers from these issues with the crankshaft breaking just behind the snout back to the #3 rod journal. We’ve seen these failures on everything from mildly modified daily drivers to full-blown competition engines with internally balanced aftermarket billet cranks. There is just something to do with the Duramax engines’ harmonics at higher rpm and bigger power levels that causes a lot of stress on the crank due to the factory firing order.

To understand why this modification is crucial, it’s important to consider the Achilles’ heel of the Duramax engine: its crankshaft. Known to typically fail in the space behind the snout back to the rod journal for the No. 3 cylinder, the crankshaft’s vulnerability is exacerbated by engine harmonics at higher horsepower levels. By altering the firing order, engine builders aim to disperse forces throughout the crankshaft, effectively moving energy rearward where it can be absorbed by the flexplate. This strategic energy dispersion is vital for preventing the internal rattling that intensifies with rpm.

While changing the firing order doesn’t result in significant power gains, it plays a pivotal role in enhancing the stability and longevity of the engine. Duramax builders are dedicated to developing camshaft profiles that manage this force dispersion as efficiently as possible, although specific camshaft details remain closely guarded secrets.

What is the general industry perspective?

Experts and engine builders in the industry focus on developing camshaft profiles that effectively manage the distribution of energy within the engine, although specific details of these profiles are closely guarded secrets.

What is the impact on power gains?

Unlike cam swaps in gas engines, altering the firing order in a Duramax engine doesn’t result in significant power increases. The primary benefit is enhanced engine stability rather than additional horsepower.

How does the alternate-firing camshaft help alleviate the problem?

By modifying the firing order to an alternate sequence, the forces exerted on the crankshaft are more evenly distributed. This adjustment shifts the energy away from the vulnerable front end of the crank, allowing it to be absorbed by other parts like the flexplate.

Why do these failures occur?

Engine harmonics are the main culprits behind these failures. In high-performance Duramax engines, the internal vibrations increase with RPM, contributing significantly to crankshaft stress and eventual failure.

What is the specific issue with the Duramax crankshaft?

The Duramax crankshaft is particularly vulnerable to failure, especially in the section behind the snout extending to the No. 3 rod journal. This area tends to suffer the most in terms of structural integrity.

What are the potential drawbacks or risks associated with using an alternate-firing camshaft on a used crankshaft?

When considering using an alternate-firing camshaft, it’s important to weigh the potential risks, especially if paired with a used crankshaft. A primary concern is that used crankshafts have already adapted to the stress of a standard firing sequence. Introducing a new firing order can introduce unfamiliar stresses, which might increase the likelihood of crankshaft failure.

Even though new crankshafts can also face challenges, opting for a billet, narrow-rod crankshaft design may offer enhanced durability. This design increases the strength at critical stress points, reducing the risk of breakage and improving harmonic performance. However, it’s important to note that no solution is foolproof, and mindful consideration should be given to the choice of components to ensure optimal performance and safety.

How do major crankshaft companies contribute to the development of alternate-fire camshafts for Duramax engines?

How Major Crankshaft Companies Innovate Alternate-Fire Camshafts for Duramax Engines

Major crankshaft manufacturers play a pivotal role in advancing alternate-fire camshafts for Duramax engines by leveraging their engineering expertise and industry insights. These companies invest in research and development to create camshaft designs that enhance engine performance across various applications.

Collaboration and Expertise

Research and Design: Crankshaft companies apply cutting-edge technology and engineering principles to design camshafts that deliver improved performance. They analyze engine dynamics and explore alternate firing orders that optimize power delivery and efficiency.
Collaboration with Engine Builders: These companies often collaborate with engine builders and technical advisors. This partnership ensures that the camshaft designs are tailored to meet specific performance goals and engine configurations.
Customization and Testing: Through rigorous testing and customization, these manufacturers fine-tune camshaft profiles to ensure compatibility and performance. This often involves adapting designs to cater to different stages of engine tuning and various performance levels.
Technical Consultation: To help customers select the optimal camshaft, major companies provide expert consultation services. This guidance is crucial for understanding how alternate-fire configurations can enhance specific engine builds, ultimately ensuring that users make informed decisions.

Major crankshaft companies’ expertise and detailed development processes contribute significantly to the evolution of alternate-fire camshafts, thereby driving improvements in Duramax engine performance.

What impact does an alternate-firing camshaft have on power gains in diesel engines compared to gas engines?

In our early engine dyno testing in 2009-2010, we immediately noticed a much smoother idle along with a noticeable difference in engine tone at higher RPMs. To date, the biggest horsepower we’ve seen from this camshaft over a stock cam is about 28 hp on the engine dyno. But this wasn’t developed with more horsepower in mind. We were really looking to improve durability at higher horsepower levels, which this technology has done.

However, it’s important to note that, unlike gas engines, this type of cam swap does not promote major power gains in diesel engines. The primary benefits in diesel applications lie in enhanced engine longevity and stability rather than sheer power output.

For diesel enthusiasts, this alternate-firing camshaft delivers where it counts by increasing the engine’s resilience and maintaining performance under higher stress, making it a valuable upgrade even without the significant power boost typical in gas engines. This balance of benefits ensures that your engine not only runs smoother but also withstands the demands of higher horsepower levels over time.

How does the effect of a cam swap on power gains in diesel engines compare to that in gas engines?

The cam swap in diesel engines does not result in major power increases, which contrasts with the more substantial power gains that can be achieved in gas engines through similar modifications.

Does an alternate-firing camshaft promote power gains in diesel engines compared to gas engines?

The alternate-firing camshaft does not lead to significant power gains in diesel engines, unlike the potential effects seen with gas engines.

Why are specific details about camshaft profiles often not shared by builders?

While we would love to give specific examples of each of our customer’s accomplishments, many are competing against each other and we need to keep some of that information to ourselves. This confidentiality is not just about maintaining privacy; it’s about preserving the competitive edge that each builder meticulously cultivates.

In the world of engine building, every camshaft profile is a closely guarded secret. These profiles are akin to a master chef’s signature recipe—they are developed to optimize performance and efficiency uniquely. Sharing such details could level the playing field, erasing the advantage that comes from years of innovation and fine-tuning.

The camshaft, a crucial component, dictates how an engine breathes and performs. Builders tirelessly work to create profiles that maximize power and efficiency, tailored to the specific demands of their engines. Therefore, protecting these innovations is vital to staying ahead in a highly competitive landscape.

In essence, while we celebrate the successes of our clients, the specifics of their technical triumphs remain closely held secrets, ensuring they continue to lead in their respective arenas.

What is the technical significance of camshaft profiles?

Camshaft profiles are vital in ensuring the efficient and balanced dispersion of power. Builders meticulously design these profiles to maximize engine efficiency and performance, underscoring their technical importance in the automotive industry.

Why are camshaft profiles considered confidential?

Camshaft profiles are a closely guarded secret because they provide builders with a significant competitive advantage. Their unique configurations are crucial to achieving optimal engine performance, making them a key differentiator among competitors.

Can an alternate-firing camshaft completely prevent Duramax crankshaft failures?

This camshaft design is not the “golden ticket” to guarantee your engine won’t fail, as your choice of other parts, assembly, and tuning is just as vital. While alternate-firing camshafts can significantly reduce harmonics and help extend bearing life, they are not the ultimate solution for preventing crankshaft failures. There have been instances where crankshafts have broken even with these cams installed.

Key Points to Consider:

Harmonic Reduction: The unique design helps in minimizing engine vibrations, contributing to smoother operation.
Bearing Longevity: By reducing stress on engine components, these camshafts can enhance bearing life.
Limitations: Despite these benefits, crankshaft failures can still occur, highlighting the importance of comprehensive engine maintenance and quality assembly.

Ultimately, while they play a crucial role, relying solely on alternate-firing camshafts for complete engine protection is not advisable. A holistic approach, considering all engine components and tuning, is essential for optimal performance and reliability.

Are alternate-firing camshafts a complete solution for preventing crankshaft failures?

No, alternate-firing camshafts are not a comprehensive solution for preventing crankshaft failures. While they offer some benefits, they are not a guarantee against such issues.

Can crankshaft failures still occur with alternate-firing camshafts installed?

Yes, crankshaft failures can still occur even when alternate-firing camshafts are installed; they do not completely eliminate the risk of such failures.

What are the specific benefits of an alternate-firing camshaft?

An alternate-firing camshaft helps to reduce engine harmonics and extends the life of the bearings, contributing to smoother engine operation and potentially increased longevity.