Aftermarket performance headers are a manifold specifically designed for performance. During design, engineers create a manifold without regard to weight or cost but instead for optimal flow of the exhaust gases. This design results in a headers that are more efficient at scavenging the exhaust from the cylinders. Headers are generally circular steel tubing with bends and folds calculated to make the paths from each cylinder's exhaust port to the common outlet all equal length, and joined at narrow angles to encourage pressure waves to flow through the outlet, and not back towards other cylinders. In a set of tuned header 's the pipe lengths are carefully calculated to enhance exhaust flow in a particular engine revolutions  per minute range.

Headers are generally made by performance  aftermarket automotive companies, but sometimes can be bought from the high-performance parts department at car dealerships . Generally, most performance car enthusiasts buy performance aftermarket headers made by companies solely focused on producing reliable, cost-effective well-designed headers specifically for their car. performance Headers can also be custom designed by a custom shop. Due to the advanced materials that some  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. In most production engines, the manifold  is an assembly designed to collect the exhaust gas from two or more cylinders into one pipe. Manifolds are often made of cast iron in stock production cars, and may have material-saving design features such as to use the least metal, to occupy the least space necessary, or have the lowest production cost. These design restrictions often result in a design that is cost effective but that does not do the most efficient job of venting the gases from the engine. Inefficiencies generally occur due to the nature of the combustion engine and its cylinders. Since cylinders fire at different times, exhaust leaves them at different times, and pressure waves from gas emerging from one cylinder might not be completely vacated through the exhaust system when another comes. This creates a back pressure and restriction in the engine's exhaust system that can restrict the engine's true performance possibilities.

• custom performance headers
• performance headers are usually add-ons
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