Does A 5.9 Valve Cover Fit N A 6.7? Here’s What You Need To Know

You are probably one of millions who tinker with your Cummins engine, wondering if Does a 5.9 Valve Cover Fit n a 6.7? There must be a million guys around who want to know, are different model parts the same and can they swap in as a substitute?

Sure, the 5.9L Cummins and 6.7L Cummins engines are rock-solid powerhouses installed inside the Dodge Ram 2500 and 3500 trucks, so what would stop their parts from intermixing, eh?

Well, the truth of the matter is a bit more complicated than that. It does not fit onto a 6.7 engine quite so easily, after all, to take a 5.9 valve cover. There’s a couple of significant reasons why these engines are non-interchangeable.

Here in this article, we will explain why a 5.9 valve cover doesn’t fit on a 6.7 engine, things you should know concerning the compatibility of these engines, and the ways of avoiding costly mistakes in your truck.

Table of Contents

Understanding the Differences Between the 5.9L and 6.7L Cummins Engines

In understanding whether or not the 5.9 valve cover can be mounted on a 6.7 engine, it would first be good to identify the difference between the two engines.

While they both happen to be inline-six turbocharged diesels and used in Dodge trucks, the 5.9L Cummins was eventually discontinued for the 6.7L back in 2007 and this transition introduced many key design upgrades.

This one’s simple and reliable: it just has the 5.9L Cummins in its chest, making a good, solid amount of horsepower and torque-a favorite for both work trucks and performance enthusiasts alike. The 5.9 is a no-frills deal with fewer emission-related components and a much more straightforward engine layout.

On the other hand, is the 6.7L Cummins-the latest, most refined engine built to meet more stringent emissions. More power and torque in the 6.7 engine is expected but with added features to meet new regulations, including better EGR systems and crankcase ventilation, among others.

This change in design makes this one of the major causes the 5.9 valve cover will not fit over the 6.7 engine, and also the reason to easily interchange the two units that should not be so easily interchanged.

Does a 5.9 Valve Cover Fit in a 6.7? Let’s Break It Down

Now, let’s get to the heart of the matter: does a 5.9 valve cover fit n a 6.7? In short, the answer is no—at least not without some significant modifications. Here’s why:

Size and Mounting Differences

Most clearly, the first reason the 5.9 valve cover does not fit is that the two engines have different physical sizes. In general, the 6.7L Cummins is a larger engine design, and its parts such as the valve cover would be built to support its larger size.

The mounting points—the places where the valve cover bolts onto the engine—are different between the two engines, so a 5.9 valve cover won’t line up properly with the 6.7 engine. That is to say, it’s nearly impossible to simply bolt on a 5.9 valve cover without some serious modifications.

Emissions and Ventilation Systems

Another important factor is the difference in emissions systems. The 6.7L Cummins has a more complex emissions setup compared to the 5.9L. This includes things like an EGR system and additional ventilation ports that are integrated into the 6.7 valve cover. These features help the 6.7 engine meet modern emissions standards and keep everything running smoothly.

However, the 5.9 valve cover was designed prior to the institution of these emission regulations so that it lacks the key features necessary for the advanced system of the 6.7. Utilizing the 5.9 valve cover with the 6.7 will therefore leave off some integral elements, and this is potentially going to cause serious oil flow and ventilation problems along with significant damage to the engine performance.

Oil Flow and Engine Ventilation

A valve cover doesn’t just cover the top of the engine; it is an important part of how oil flow is managed and how the engine is ventilated. The 6.7 valve cover has been designed to accommodate the oil flow requirements and pressure management necessary for the larger, more powerful engine. It also has specific ports to help manage crankcase ventilation in line with the 6.7’s more complex emission systems.

The 5.9 valve cover was designed for an engine with simpler oil and ventilation needs. If you were to use it on a 6.7 engine, you might run into issues where the oil flow is restricted or the ventilation doesn’t work properly, leading to potential engine damage or reduced performance.

Can You Modify a 5.9 Valve Cover to Fit a 6.7?

It’s true that for most truck nuts, modifying parts is the fun part, but trying to adapt a 5.9 valve cover to fit on a 6.7 isn’t easy. You can attempt to drill new bolt holes and adapt the cover for it to fit, but it’s not straightforward by any means.

Even modified, the 5.9 valve cover wouldn’t have the ports and fittings for the more advanced emissions and oil management systems found on the 6.7 engine. In short, yes, it may be technically feasible to make a 5.9 valve cover work on a 6.7 engine.

However, in general, not recommended because the risk of undermining your engine’s performance and further damaging vital components is quite high.

Frequently Asked Questions About Valve Cover Compatibility

Can I Use a 5.9 Valve Cover on a 6.7 Engine?

The simple answer is no. The 5.9 valve cover is not compatible with the 6.7 engine due to differences in size, mounting points, and the engine’s emissions and ventilation systems. It’s best to stick with the 6.7 valve cover designed specifically for that engine.

What Happens If I Try to Use the Wrong Valve Cover?

Using the wrong valve cover can lead to oil leaks, poor ventilation, and even engine damage over time. The valve cover is an essential part of keeping your engine properly lubricated and ventilated, so using one that’s not designed for your engine can result in serious issues.

Why Does the 6.7 Valve Cover Look Different from the 5.9?

The 6.7 valve cover is designed with extra components to accommodate the 6.7 engine’s more complex emissions system, including additional ports for crankcase ventilation and exhaust gas recirculation. The 5.9 valve cover doesn’t have these features, as it was designed for an older, simpler emissions setup.

Is It Worth Modifying a 5.9 Valve Cover for a 6.7?

It’s not advisable. While it’s possible to modify a 5.9 valve cover to fit a 6.7 engine, doing so is risky and could lead to serious performance and reliability issues. It’s best to use the correct valve cover for your engine.

Conclusion

Well, does a 5.9 valve cover fit on a 6.7? No, and reasons for that lie in differences between these two engines are quite vast. The 6.7L Cummins is bigger and more complex. It has an emissions system as well as oil management capabilities.

The 5.9 valve cover is not engineered for that. If you want to keep your engine running in the best condition and prevent possible problems, it’s always better to use the valve cover specifically designed for your engine model.

Therefore, knowing these key differences and why the right parts need to be used will enable your 6.7 engine to run at the best it can for as long as possible.