I’m not a major fan of open headers.
They’re deafeningly loud. So loud in fact you can barely hear the person sitting right next to you. Why are they so loud?
Because an open header removes everything designed to dampen the sound coming from an engine, from the catalytic converter down to the muffler.
Which leads to the second reason why I don’t like open headers which I’ll get into later.
But within the right context running open headers has advantages that can’t be ignored. Open headers won’t hurt your engine if you get a tune on a fuel injected engine or tweak the carburetor on a carbureted engine.
Keep reading to find out the pros and cons of open headers to determine if running open header is the right move for you.
What Are Open Headers?
Open headers means that an engine’s exhaust gases and fumes only run through the exhaust headers – there’s no catalytic converter, resonator, exhaust pipe or muffler.
With the main components of the exhaust system eliminated from the equation, there’s no back pressure and emissions are allowed to blow straight into the atmosphere.
Headers are among the most straightforward bolt on upgrades you can make on any vehicle if you don’t mind getting your hands dirty.
Most vehicles come stock with exhaust manifolds which while they get the job done of expelling exhaust gases and fumes from the cylinders after combustion. They’re not so great about getting those exhaust gases out fast.
High performance aftermarket headers work to make exhaust flow less restrictive. Drag cars use open headers to maximum affect to deliver maximum performance.
The longer exhaust gases linger in an engine’s combustion chamber, the longer it takes for the next combustion cycle to happen – this is what robs an engine of performance.
Let’s turn our attention now to some of the differences between headers and stock manifolds. Because although they do the same job, they do them in slightly different ways.
Headers vs. Manifolds
The big difference between aftermarket headers and stock exhaust manifolds is the manufacturing process.
Manifolds are made of solid iron with a port for each cylinder to expel exhaust gases and fumes. Headers on the other hand are made of steel with a dedicated pipe for each cylinder.
The Epic Journey of Exhaust Gases
More so with headers, exhaust gases travel from the cylinder in the combustion chamber out to each individual pipe where they meet together at the collector before going through the rest of the exhaust system.
From the collector the gases travel to the catalytic converter where these toxic gases and fumes get cleaned.
As the gases continue passing through the exhaust system, they may flow into what’s called a resonator which works to quieten the sound of the moving exhaust gases.
Then the gases flow into the muffler where the sound of the moving gases is quietened even more before they flow out through the tail pipe into the atmosphere.
Or at least this is the path they would take.
Running open headers removes everything about the exhaust system except the manifold or headers. Which means exhaust gases get expelled straight into the atmosphere once they come into the collector.
Open Headers vs. Straight Pipes
If open headers removes all parts of the exhaust system after the headers. Then what’s meant by the term, straight piping?
A straight pipe is similar to open headers in that elements like the catalytic converter, resonator and muffler are gone.
Instead, there’s just one (or two) long pipes stretching from the headers to the exhaust tips with no catalytic converter, resonator or muffler between them. In other words, there’s just one (or two) long straight pipe(s).
Even though there’s a pipe connected to the headers, there’s no catalytic converter, resonator or muffler. Which means that like open headers this exhaust system is also incredibly loud.
Like open headers the advantage of straight pipes is that it helps the engine run more efficiently by removing the back pressure created by elements like a catalytic converter and a muffler.
What you get is more horsepower, torque and responsive acceleration. And you might even notice a slight uptick in fuel efficiency.
Another benefit of running open headers or a straight pipe is weight reduction. Without items like the catalytic converter, resonator or muffler weighing you down. Your vehicle can fly down a straight line faster than ever.
Open Headers and Horsepower
Most stock exhaust systems are not able to get rid of a sufficient volume of exhaust gas at high engine speeds.
Restrictions to the flow of exhaust gas are the catalytic converter, resonator and muffler, along with all the exhaust pipes routing the gases to the exhaust tips.
Good aftermarket headers have bigger pipes to push out a larger volume of exhaust gases.
A major advantage to running open headers is that it has the potential of giving your engine an incredible 30 to 40 horsepower boosts, depending on displacement.
Compare that to the 6 to 20 horsepower you might gain if the headers are connected to the rest of the exhaust system.
These figures may not sound that impressive. But like with weight savings, every pony counts.
When you remove the rest of the exhaust system, the result is more horsepower. That’s why an engine with an eight cylinder displacement will gain more horsepower from running open headers than an engine with a four cylinder displacement.
Will Open Headers Burn Valves?
Valves have two jobs: to let air into the cylinders and to let exhaust gases out.
Depending on an engine’s design it’ll have two to four valves per cylinder. High output engines usually come with four valves per cylinder. So, a four cylinder engine has sixteen valves and an eight cylinder engine has twenty four valves.
Since there are two jobs for valves to do, there are two types of valves: intake and exhaust.
The intake valves are responsible for allowing air and fuel into a cylinder where the uniting of these elements causes combustion.
The byproduct of combustion is exhaust gases and fumes.
Exhaust valves are in charge of providing those exhaust gases and fumes an escape from the combustion chamber.
But if either of the valves should happen to get too hot, the result is a burnt valve. A burnt valve can’t seal a cylinder completely – this is where loss of compression comes from.
Burnt valves result in engine performance problems like check engine lights, a rough running engine and misfiring.
Since replacing a stock manifold with headers provides more room for the exhaust gases and fumes to escape at a greater volume. It can alter the engine’s air-to-fuel ratio.
Which means that the timing for the valves to open and close needs to change otherwise the result will be – burnt valves. This is where tuning comes into play.
Do Open Headers Require a Tune?
Even if you’re running open headers, or maybe I should say especially if you choose to run open headers, it changes the exhaust aspirations of an engine.
Given the explanation of how valves in an engine work. The logical conclusion is that you should follow up the installation of headers (even if going open headers) with a tune.
What do we mean by tune?
An ECU is the computer in a modern vehicle. A car, for example, has many ECUs all programmed for different functions within the automobile.
But the one that’s most important when it comes to headers is the one used to control the functions of the engine.
By reprogramming this ECU which is sometimes called reflashing, you can change the parameters of when, for instance the engine valves open and close to compensate for the fact that the freshly installed headers are allowing a greater volume of exhaust gas to escape the engine.
Not only does tuning give you a more efficient engine. But you won’t burn your valves.
Are Open Headers Even Legal?
Unless you’re at a race track or a car show, running open headers on public streets is illegal. Many cities, towns and municipalities have sound ordinance that limit the amount of noise a vehicle is allowed to make.
For example, near the area we live because there are so many surrounding businesses. Eighteen wheelers are prohibited from using engine brakes or Jake brakes.
An engine brake opens the exhaust valve in a diesel engine to slow a big truck like a semi-trailer down without using the brake pedal which conserves the air brakes.
When a driver uses the Jake brake it emits a loud noise that can be described as rolling over a rumble strip.
It’s not a harsh, loud sound like open headers. But its loud enough to interrupt business operations and families in their homes.
Open Headers and Emissions
Not only do many state governments in America have noise limits. Many states have emissions standards that a vehicle must meet in order to be considered legally road worthy.
Those standards are determined by the Clean Air Act, which is another big reasons why I’m not a huge fan of open headers.
You see, since I was a teenager, I’ve always liked modifying my vehicles so that they’re still street legal – I like the versatility of using my car to slay opponents on the track, then driving home legally on public streets.
Racing with Open Headers
Besides increased performance, and the louder sound. One of the biggest differences you’re going to experience with open headers is the smell.
The purpose of the catalytic converter is to filter out the harmful byproducts inherent in exhaust gases and filter them out as the exhaust gases make their way out through the tail pipe.
But without the catalytic converter in place to do its job, those harmful emissions get dumped out into the atmosphere from right where the driver is sitting.
And that’s the other reason why I’m not a fan of open headers.