Exhaust Manifolds Vs. Headers
What Are Exhaust Manifolds?
Exhaust manifolds channel exhaust away from the cylinder head to the exhaust pipe and eventually out the back of the vehicle. They are frequently formed of cast iron in a block-like configuration.
Cast iron gives exhaust manifolds sturdiness and longevity. Because the cast iron material is thick, it holds on to heat well, which is good for emissions and keeps heat from leaking to other nearby parts.
The thick walls do, however, mean there is a small space for exhaust gases to pass through, and the iron casting makes the interior rough, which can slow the flow of exhaust gases. This slow flow of gases creates back pressure, which keeps the exhaust from being cleared as efficiently as possible. This reduces the efficiency and ultimately the power of the engine, because exhaust must go out to allow fresh fuel and air in.
What Are Headers?
Headers are intended to solve the engine efficiency and power setbacks of the exhaust manifold. Headers are basically aftermarket upgrade exhaust manifolds for performance applications. They use an individual steel tube for each cylinder. These tubes all connect to a collector pipe. The tubes are smooth and equal in length, and this ensures that the gases from each cylinder reach the collector separately, avoiding back pressure.
Header Pros and Cons
The benefit of smooth and equal tubes to avoid back pressure can be lost if other exhaust components are not also upgraded. If the exhaust pipe that follows the headers is too restrictive, it can introduce back pressure to the exhaust system and diminish the power advantage of headers. Another disadvantage of headers is that, due to their thinner walls, they do not absorb as much sound as cast iron exhaust manifolds, making them louder (although some may see this an advantage).
Can Headers Come from Stock?
Some vehicles do come with tubular steel manifolds from stock. Primarily, these are for performance vehicles, such as sports cars. Jeep also notably uses tubular steel exhaust manifolds.
