Join any conversation regarding high performance engines, and there’s a good chance you’ll hear the word “headers” used quite a bit.
That’s because a good set of exhaust headers is one of the first fundamental upgrades a gearhead will make to their engine to improve its power output and performance. Let’s explain why.
What Are Exhaust Headers?
Exhaust headers are part of a performance exhaust system.
Comprised of smoothly-bent tubing sections, headers bolt directly to the engine, specifically the cylinder head’s exhaust ports, and are the first part of the path that exhaust gasses pass through on their way out of the engine.
Headers replace the stock exhaust manifold(s).
From the factory, most vehicles are fitted with an exhaust manifold that, while reliable, may feature restrictive bends, abrupt diameter changes, and a rough interior casting finish that can inhibit the flow of the exhaust gasses as they leave the engine.
More importantly, a factory-equipped exhaust manifold often merges the exhaust flow from each cylinder rather quickly—almost immediately after leaving the individual exhaust ports on the engine.
A good set of long tube exhaust headers will allow the gasses from each cylinder to pass down a long primary section before mixing with the gasses from the other adjacent cylinders. Again, this helps promote better flow—we’ll talk more about that in a sec.
And that’s the key distinction here: Compared to the stock exhaust manifold, the goal of an exhaust header is to improve the flow of exhaust gasses out of the engine. And to understand why better flow is important, keep reading…
How Exhaust Headers Improve Engine Performance
If you’re picking up a trend here, it’s that, generally speaking, better flow equals better performance. Think of your engine like a big, fancy air pump: The more air it can move in—and out—the better.
Now, there are a handful of ways smart engine builders improve airflow. A performance air intake helps, along with a good cylinder head design. The final step, obviously, is getting the spent exhaust gasses out.
And that journey begins with the header.
We’ve alluded to the benefits of having long, sweeping bends in the header primary tubes (the individual pipes from each cylinder port, often just called “primaries”) and the value of having a smooth transition between tubing sections. If you’ve ever sucked soda through a bendy silly straw as a kid, you know it takes a lot of extra effort. Well, the same basic principle applies here too.
But there is also some more complex science to understand as well.
Thanks to the nature of the engine ignition cycle, your exhaust system flows in pulses. In a manifold, all those pulses are quickly mixed together, creating turbulence in the manifold and, again, impeding flow.
Conversely, a good header design uses specially-matched primary tubing sections to ensure that each cylinder pulse arrives in the collector at a specific time, so the exhaust flow is evenly mixed and uninterrupted.
As an added bonus, it can actually improve the airflow INTO the engine—we call that the “scavenging” effect.
Headers & Exhaust Scavenging
Properly deisgned headers help exhaust gas leave the cylinder, which in turn helps pull a fresh air/fuel mixture into the cylinder head to start the whole process over again.
Here’s how it works: Since exhaust gases escape the cylinder very quickly, the high-speed pulse moves down the header tube and creates a low pressure spot behind the initial pulse. The resulting low pressure vacuum helps draw new air back into the engine.
This ultimately leads to the engine operating more efficiently—which directly results in improved performance. We wrote a far more in-depth article on this subject, so if you want an elaborate explanation of the exhaust scavenging phenomenon, check this story out:
Some Considerations When Buying & Installing Headers
For starters, headers are part of your vehicle’s exhaust system which, depending on where you live, might mean that you’ll have a significant amount of regulations regarding exhaust system modifications and emissions requirements.
In other words, before you select the best headers for your specific vehicle, make sure to check with your local laws and regulations regarding exhaust system modifications.
Another thing to consider, you’ll often have to relocate the exhaust oxygen sensor, which for modern ECU-controlled engines, can alter the readings from a downstream O2 sensor. That often results in a check engine light, which might be remedied by a simple code reader/scan tool reset, or by installing a spacer onto the physical O2 sensor itself.
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A set of exhaust headers is a smart step on the path to bigger performance gains, and is the perfect complement to an air intake, cat-back exhaust, and high performance cylinder heads.
That said, performance exhaust technology is a complex, nuanced topic—so we’ve put together some more articles on related subjects to help you out. If you really want to go down the rabbit hole of exhaust system performance, give these posts a read too:
- Will These Exhaust Headers Fit my Vehicle?
- A Beginner’s Guide to Aftermarket Exhaust Systems
- How To Choose an Aftermarket Exhaust System
- An Introduction to Exhaust System Components
- How Does an Exhaust Pipe Affect Engine Performance?
- How Much Horsepower Does a Dual Exhaust Add?
- What is the Purpose of a Crossover Pipe on an Exhaust?
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