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When working on Cummins diesel engines, especially the popular 5.9L and 6.7L models, one question that often arises is whether parts from one engine can fit into the other. A common inquiry involves the valve covers—does a 5.9 valve cover fit n a 6.7? While it might seem like a simple swap, there are key differences between these two engines that make the direct fitment of a 5.9 valve cover onto a 6.7 engine a bit more complicated. This article will explore these differences and the modifications required to make the swap, so you can make an informed decision about whether it’s the right choice for your engine.
Understanding the Engines
To understand why the 5.9L valve cover doesn’t easily fit on a 6.7L engine, it helps to know the differences between these two popular Cummins diesel engines.
- 5.9L Cummins Engine: The 5.9L engine was produced from 1984 to 2007 and is widely praised for its durability and reliability. It’s commonly found in Dodge Ram trucks and is often favored by diesel enthusiasts for its simplicity and performance. The engine features a straightforward design, with fewer components than the 6.7L version, making it easier to work on and modify.
- 6.7L Cummins Engine: The 6.7L engine was introduced in 2007 and continues to be used in newer Ram trucks. It features a larger displacement, which allows it to produce more power and torque. The 6.7L also comes with more advanced emissions components, like a crankcase pressure sensor and additional sensors for improved fuel efficiency and reduced emissions. These differences in design and size play a role in why the 5.9L valve cover isn’t a perfect fit on the 6.7L engine.
Valve Cover Basics
Before we dive into the compatibility issues, it’s important to understand the function of a valve cover.
- What Does a Valve Cover Do? A valve cover is an essential component of the engine that sits on top of the cylinder head. It seals the top of the engine, keeping the oil inside the engine while also preventing debris from entering the valve train. Additionally, the valve cover helps maintain proper engine pressure and can be equipped with breathers or vents to regulate airflow.
- Key Differences in Valve Covers: Both the 5.9L and 6.7L valve covers serve the same basic function but differ in their design due to the changes made in the engine architecture. The 6.7L valve cover is designed to accommodate extra sensors and has a different shape and bolt hole pattern compared to the 5.9L valve cover. These differences make swapping the covers between the two engines challenging.
Key Compatibility Factors
When considering whether a 5.9L valve cover can fit on a 6.7L engine, several factors need to be considered:
- Bolt Pattern and Size: The bolt hole patterns on the 5.9L and 6.7L engines are not identical. The 6.7L engine uses a different mounting system to account for the additional components found in the engine. While both engines may have similar overall dimensions, the precise alignment of the valve cover is critical for a proper seal, and differences in the bolt pattern can prevent the 5.9L valve cover from fitting without modification.
- Crankcase Pressure Sensor: One significant difference between the 5.9L and 6.7L valve covers is the crankcase pressure sensor found on the 6.7L. This sensor monitors pressure in the crankcase, which is a critical part of the 6.7L’s emission system. Since the 5.9L valve cover was not designed to accommodate this sensor, a 5.9L valve cover would either need to be modified to fit the sensor or the sensor would need to be relocated or plugged.
- Breather and Oil Drain Tubes: The breather and oil drain tubes also differ between the two engines. If you’re using a 5.9L valve cover on a 6.7L engine, you’ll need to replace these components or modify them to ensure proper function and avoid oil leaks.
Modification Requirements
In some cases, people may attempt to use a 5.9L valve cover on a 6.7L engine, but there are modifications required to make it work:
- Breather and Oil Drain Tubes: The breather system and oil drain tubes in the 5.9L engine are different from those in the 6.7L. You would need to source the proper tubes for the 5.9L engine or make adjustments to fit the 6.7L setup.
- Crankcase Pressure Sensor: The crankcase pressure sensor on the 6.7L is an important part of the emissions system. If you’re trying to use a 5.9L valve cover, you would either need to modify the cover to accommodate the sensor or find a way to bypass or relocate it.
- Tools and Expertise: These modifications may require basic mechanical tools and expertise in engine work. Depending on your experience, you may need to enlist the help of a professional mechanic to ensure proper fitment and functionality.
Challenges of Using a 5.9 Valve Cover on a 6.7
Even with modifications, using a 5.9L valve cover on a 6.7L engine presents some challenges:
- Risk of Oil Leaks: Since the 5.9L valve cover wasn’t designed for the 6.7L, there is a higher risk of improper sealing, which could lead to oil leaks. A poor seal could result in oil dripping onto hot engine components, which could cause damage or a fire.
- Sensor Compatibility: The absence of space for the crankcase pressure sensor and other emission sensors in the 5.9L valve cover can lead to issues in engine performance and emissions control. You may also need to install extra components to make up for the missing sensors.
- Increased Labor: The amount of labor required to make a 5.9L valve cover fit on a 6.7L engine may not be worth the effort. You would have to address various challenges related to sensor alignment, sealing, and oil flow, which could take a significant amount of time and expertise.
Alternative Options
If you’re not keen on dealing with the complexities of modifying a 5.9L valve cover for a 6.7L engine, there are some alternative options:
- Aftermarket Valve Covers: Aftermarket companies offer valve covers designed to fit both the 5.9L and 6.7L engines. These covers are typically designed with the necessary sensor ports and proper fitting, ensuring a more straightforward installation without the need for modifications.
- Using the Correct Valve Cover: If you want the best performance and the least amount of hassle, the best option is to use the valve cover specifically designed for the 6.7L engine. This ensures compatibility with all the components, including sensors and tubing.
Expert Opinions and Real-World Experiences
Mechanics and diesel enthusiasts generally recommend using the correct parts for the engine. While some have successfully made the swap with modifications, it’s important to consider the potential risks, such as oil leaks, sensor issues, and the time involved in making the swap work.
Many people who attempt this swap report mixed results. Some have found success, while others experienced complications like sensor misalignment or sealing issues. It’s always a good idea to consult with an experienced mechanic or refer to forums where others have shared their experiences.
Conclusion
So, does a 5.9 valve cover fit n a 6.7 Cummins engine? The answer is yes, but with significant modifications. The two engines have different design characteristics, including bolt patterns, sensor requirements, and breather tube configurations, making the swap difficult without adjustments. While it’s possible to make it work, it’s not ideal due to the complexity and potential risks, such as oil leaks and sensor issues.
If you’re considering this swap, it’s worth weighing the time, effort, and potential for problems. In most cases, using a valve cover specifically designed for the 6.7L engine or opting for an aftermarket cover is a better and safer choice.
FAQs
Can I use a 5.9L Cummins valve cover on a 6.7L engine without modifications?
No, a 5.9L valve cover will require modifications, such as sensor adjustments and replacing oil drain tubes, to fit on a 6.7L engine.
What modifications are needed to fit a 5.9L valve cover onto a 6.7L engine?
You’ll need to modify or replace the crankcase pressure sensor, breather tubes, and oil drain tubes to make the 5.9L valve cover compatible.
Are aftermarket valve covers available for both 5.9L and 6.7L Cummins engines?
Yes, aftermarket valve covers are designed to fit both engine models, providing a hassle-free solution without the need for modifications.
What risks come with using a 5.9L valve cover on a 6.7L engine?
Using a 5.9L valve cover can lead to oil leaks, sensor misalignment, and potentially affect engine performance if not properly modified.
Is it better to use a 5.9L valve cover or a 6.7L valve cover on a 6.7L engine?
It’s best to use a 6.7L valve cover, as it’s specifically designed to fit, ensuring proper sealing and sensor compatibility without requiring modifications.
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