When it comes to truck engines, particularly the legendary Cummins engines, enthusiasts often find themselves asking: “Does a 5.9 valve cover fit on a 6.7?” This might seem like a simple question, but it’s one that has sparked countless debates in garages and online forums. Whether you’re considering a valve cover swap for aesthetics, function, or curiosity, let’s dive into the details.
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ToggleWhat Are the 5.9 and 6.7 Cummins Engines?
Before we answer the big question, let’s start with some context. The 5.9L and 6.7L Cummins engines are two of the most popular diesel engines found in Dodge Ram trucks. The 5.9L, which was in production from 1989 to 2007, gained fame for its reliability and simplicity. The 6.7L, introduced in 2007, brought more power and modern features to the table.
While these engines share many similarities, they also have distinct differences in terms of size, design, and components—including valve covers. Understanding these differences is key to knowing whether a 5.9 valve cover can work on a 6.7 engine.
Physical Differences Between the 5.9 and 6.7 Valve Covers
The valve cover is more than just a piece of metal or plastic that sits on top of your engine. It’s designed to seal the top of the engine, keep oil from leaking, and protect internal components. While the 5.9 and 6.7 Cummins engines are closely related, their valve covers are not identical.
Size and Dimensions
One of the first things to consider is size. The 6.7 engine is slightly larger overall compared to the 5.9. As a result, the valve covers have different dimensions. A 5.9 valve cover might fit onto a 6.7 engine in some cases, but it’s unlikely to be a perfect match. Even small differences in bolt placement or overall size can lead to issues.
Bolt Patterns
The bolt pattern is another critical factor. Valve covers are secured with a series of bolts, and the pattern of these bolts must align perfectly with the engine head. While the 5.9 and 6.7 share a lot of design DNA, their bolt patterns for the valve covers are not identical. This mismatch makes it difficult to swap valve covers between the two engines without modifications.
Functional Differences
Aside from size and bolt patterns, the valve covers on these engines may also have different features. For example, the 6.7 valve cover often incorporates modern design elements to accommodate emissions systems like the EGR (Exhaust Gas Recirculation). The 5.9, being an older engine, doesn’t have these considerations. This functional mismatch means a 5.9 valve cover may not meet the needs of a 6.7 engine.
For more technical insights on the differences between these engines, check out the detailed guide on Diesel World, a high-authority source for diesel enthusiasts and mechanics.
Why Do People Want to Swap Valve Covers?
You might be wondering why anyone would want to put a 5.9 valve cover on a 6.7 engine in the first place. Here are a few reasons:
Aesthetic Appeal
Many truck enthusiasts prefer the look of the older 5.9 valve covers. They often have a simpler, cleaner design compared to the more modern 6.7 covers.
Nostalgia
For those who grew up around 5.9 engines, there’s a certain nostalgia tied to the classic design. Swapping a 5.9 valve cover onto a 6.7 engine can be a way to pay homage to the older engine.
Cost and Availability
In some cases, 5.9 valve covers might be more readily available or less expensive than their 6.7 counterparts. This can make them an attractive option for budget-conscious enthusiasts.
Can You Make It Work?
If you’re set on using a 5.9 valve cover on a 6.7 engine, it’s not impossible, but it’s also not straightforward. Here’s what you need to consider:
Modifications
To make a 5.9 valve cover fit on a 6.7 engine, you’ll likely need to modify either the cover or the engine head. This could involve drilling new bolt holes, adding spacers, or making other custom adjustments. Keep in mind that these modifications can be time-consuming and may compromise the integrity of the components.
Sealing Issues
Even if you manage to attach a 5.9 valve cover to a 6.7 engine, there’s no guarantee it will seal properly. A poor seal can lead to oil leaks, which can cause serious engine damage over time. Always prioritize a proper fit and reliable seal over aesthetics or cost savings.
Emissions and Compatibility
If your 6.7 engine is subject to emissions regulations, using a 5.9 valve cover might not be compliant. The 6.7’s valve cover is designed to work with specific emissions systems, and swapping it out could lead to issues with inspections or performance.
The Final Verdict
So, does a 5.9 valve cover fit on a 6.7 engine? The short answer is no—not without modifications. While the two engines share a lot of similarities, their valve covers are not interchangeable due to differences in size, bolt patterns, and functionality.
If you’re considering this swap, be prepared for significant customization work. In most cases, it’s easier and more practical to use the correct valve cover for your engine. However, if you’re a seasoned DIY enthusiast with a passion for customization, it might be a project worth tackling.
A Better Solution
Instead of trying to force a 5.9 valve cover onto a 6.7 engine, consider looking for aftermarket options designed specifically for the 6.7. Many companies offer custom valve covers that deliver the aesthetics you want without sacrificing fit or function.
In the end, the right choice depends on your goals, budget, and mechanical expertise. Whatever you decide, make sure to prioritize the health and performance of your engine above all else. Read more