Headers are one of the easiest bolt-on accessories you can use to improve an engine's performance. The principles behind a good exhaust system are fairly basic. When exhaust gases flow out of the cylinder heads and then progress through the system, they cool and contract as they go. The goal is to get exhaust out of the system as quickly and thoroughly as possible—greater heat dissipation allows the engine to run cooler, and less exhaust in the cylinders allows more fresh air in for a better burn.

In a normal engine, once the exhaust gases exit the cylinder they end up in the exhaust manifold. In a four-cylinder or eight-cylinder engine, there are four cylinders using the same manifold. From the manifold, the exhaust gases flow into one pipe toward the ­­catalytic converter and the ­muffler. It turns out that the manifold can be an important source of back pressure because exhaust gases from one cylinder build up pressure in the manifold that affects the next cylinder that uses the manifold.

The idea behind an exhaust header is to eliminate the manifold's back pressure. Instead of a common manifold that all of the cylinders share, each cylinder gets its own exhaust pipe. These pipes come together in a larger pipe called the collector. The individual pipes are cut and bent so that each one is the same length as the others. By making them the same length, it guarantees that each cylinder's exhaust gases arrive in the collector spaced out equally so there is no back pressure generated by the cylinders sharing the collector.

To improve performance, a set of performance headers typically has thinner walls and a smoother inside finish. Not only that, custom exhaust headers look way cooler, especially when chromed or coated. Thermal-barrier coatings can improve heat dissipation on headers and exhaust components. These coatings contain either aluminum or ceramic fragments that are either baked on or electro-statically applied. In addition to improving exhaust flow, a thermal coating can also reduce heat soaking of a sensitive component such as a starter motor, which might cause it to otherwise malfunction.

When cylinders don't have to fight each other to expel their exhaust, they can put more power through the wheels, and a bigger grin on your face. Exhaust headers come in all shapes and sizes for hundreds of applications, from leading manufacturers such as Edelbrock Headers, Hedman headers, JBA headers, and Pacesetter headers. Honda headers, Toyota headers, Mazda headers, and VW headers are all now available to put the punch in your sport compact. Of course, Hedman hedders, JBA headers, and Pacesetter headers are produced in a variety of configurations for Camaro and Firebird, and musclecar headers are available for many older applications as well.

Headers are generally made by aftermarket automotive companies, but sometimes can be bought from the high-performance parts department at car dealerships. Generally, most car performance enthusiasts buy aftermarket headers made by companies solely focused on producing reliable, cost-effective well-designed headers specifically for their car. Headers can also be custom designed by a custom shop. Due to the advanced materials that some aftermarket headers are made of, this can be expensive. Luckily, an exhaust system can be custom built for any car, and generally is not specific to the car's motor or design except for needing to properly connect solidly to the engine. This is usually accomplished by correct sizing in the design stage, and selecting a proper gasket type and size for the engine.

Exhaust headers are the first link in the performance-exhaust chain, and manufacturers claim that these can add as much as 40 more usable horsepower. Aftermarket exhausts don't actually make horsepower, but they do choke off less power by reducing backpressure for better flow.

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