Does a 5.9 Valve Cover Fit on a 6.7? Key Differences and Compatibility Explained

When it comes to diesel truck engines, the 5.9 and 6.7-liter versions of the Cummins engine are popular choices, known for their power and reliability. However, if you’ve been wondering whether a 5.9 valve cover will fit on a 6.7 engine, you’re not alone. This is a common question for truck owners looking to replace or upgrade parts. In this post, we’ll break down the key differences between the 5.9 and 6.7 valve covers and help you understand whether they are interchangeable.

What Are the 5.9 and 6.7 Engines?

What is the 5.9 Engine?

The 5.9-liter Cummins engine was a staple in older Dodge Ram diesel trucks, primarily from the early 2000s to around 2007. Known for its durability, it became a favorite for heavy-duty tasks and long-distance hauling. Despite being an older engine, many drivers continue to trust the 5.9 for its strength and low maintenance needs.

What is the 6.7 Engine?

The 6.7-liter Cummins engine is a newer, more advanced version of the 5.9. Introduced around 2007, the 6.7 offers improved fuel efficiency, better emissions control, and enhanced power output. It’s typically found in newer Dodge Ram trucks and is equipped with more modern features that make it more efficient and environmentally friendly compared to its predecessor.

Although the 5.9 and 6.7 engines are similar in many respects, they differ in certain areas, particularly in design and performance.

What is a Valve Cover and Why is it Important?

A valve cover is an essential engine part that seals the top of the engine’s cylinder head. It keeps the oil inside the engine, helps maintain pressure, and prevents leaks. The valve cover also plays a role in protecting the engine’s internal components, including the valves and rocker arms.

Valve covers are crucial for ensuring the engine runs smoothly, and using the correct one is essential to avoid oil leaks, engine damage, or performance issues. But can you swap a 5.9 valve cover with a 6.7 valve cover?

Can a 5.9 Valve Cover Fit on a 6.7?

Size and Design Differences

One of the primary concerns when fitting a 5.9 valve cover on a 6.7 engine is the size and design. Although both engines are part of the Cummins family, the 6.7 engine is larger in both displacement and physical size compared to the 5.9. The valve covers for these engines are designed to match the size and structure of each engine, which means that the 5.9 valve cover may not fit on the 6.7 engine without modifications.

• Dimensions: The 6.7 valve cover is generally larger to accommodate the larger engine components and provide enough space for the increased displacement. The 5.9 valve cover is smaller and designed for the older, more compact engine layout.
• Mounting Points: The bolt holes and mounting points for the valve covers may also differ between the two engines. Even if the 5.9 valve cover physically fits on the 6.7 engine, it may not line up properly with the mounting points, leading to improper sealing and potential leaks.

Gasket and Seal Compatibility

Another important factor to consider is the gasket and seal compatibility. The gaskets on the 5.9 valve cover may not be compatible with the 6.7, leading to oil leaks and poor engine performance. Valve covers come with specific gaskets designed to fit the shape of the engine’s cylinder head, so mismatching these components could result in issues with oil retention and engine efficiency.

Key Differences Between the 5.9 and 6.7 Valve Covers

1. Physical Size

The 6.7 valve cover is designed to cover a larger engine, while the 5.9 valve cover is smaller in size. This difference in size means that trying to fit a 5.9 valve cover onto a 6.7 engine could cause misalignment, and even if it fits over the engine, it may not seal properly.

2. Mounting Points and Bolt Patterns

The mounting points for securing the valve covers might differ. While both engines have similar mounting systems, slight differences in the bolt patterns can cause issues. If the bolts don’t align correctly, you could have difficulty installing the valve cover securely, leading to leaks or improper fitment.

3. Gaskets and Seals

The gasket and seal dimensions may vary between the two valve covers. Gaskets are designed to create an airtight seal between the valve cover and the cylinder head, and using the wrong gasket can cause oil leaks, which could damage the engine over time.

What Are Your Options If a 5.9 Valve Cover Doesn’t Fit a 6.7?

If you’ve determined that a 5.9 valve cover won’t work on your 6.7 engine, there are several options available to get your engine in top condition:

1. Aftermarket Valve Covers for the 6.7 Engine

Rather than trying to fit a 5.9 valve cover, consider investing in an aftermarket valve cover that’s specifically designed for the 6.7 engine. These covers are built to match the size, bolt patterns, and gasket requirements of the 6.7, ensuring a perfect fit and long-lasting performance.

2. OEM Replacement Valve Covers

For the best possible fit and performance, consider using OEM (Original Equipment Manufacturer) valve covers for your 6.7 engine. OEM parts are designed and manufactured to meet the specifications of your engine, ensuring that everything fits as intended and works efficiently.

3. Modifications (Not Recommended)

In some cases, truck enthusiasts may attempt to modify a 5.9 valve cover to fit a 6.7 engine. However, this is generally not recommended unless you have expertise in engine modifications. Modifications can lead to improper sealing, leaks, and potential engine damage.

How to Ensure a Proper Valve Cover Fit on Your 6.7 Engine

To ensure you get the right valve cover for your 6.7 engine, follow these tips:

1. Check the Manufacturer’s Specifications: Always refer to your engine’s manual or manufacturer’s guidelines to find the exact valve cover specifications.
2. Look for Compatibility: When purchasing a new valve cover, confirm that it is specifically designed for the 6.7 engine. Some aftermarket options may claim compatibility with multiple engines, so make sure the one you choose is suitable.
3. Inspect the Gasket: Ensure the gasket is designed for your engine. The right gasket will create a proper seal and prevent oil leaks.
4. Consult a Professional: If you’re unsure about what valve cover is best for your 6.7 engine, it’s always a good idea to consult a mechanic or professional who can help guide you in the right direction.

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Conclusion

In conclusion, while it may be tempting to try swapping a 5.9 valve cover onto a 6.7 engine, it’s not recommended due to the differences in size, mounting points, and gasket compatibility. The best approach is to either go with a valve cover designed specifically for the 6.7 engine or choose a reliable aftermarket or OEM replacement.

Ensuring that you use the correct valve cover for your 6.7 engine will help keep your truck running smoothly, prevent oil leaks, and save you from costly repairs in the future.

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