It’s very satisfying to listen to your engine idling and feel its powerful vibrations. But as soon as you step on the gas and hit the road, your headers come into play. They are the first stop for exhaust gases on their way out of your cylinder heads and into the exhaust stream, and they can make or break your car’s performance.
Headers come in two types- long tube and short tube. What sets them apart is the length of the primary tubes to the collector. For “shorty headers,” the port pipes actually merge into a single exhaust pipe in a much shorter distance. For long tube headers, the exhaust pipes are much longer (about 28”) and merge farther out. Because of this, each design impacts back pressure in the exhaust system in a different way.
Longer port pipes result in lower exhaust back pressure. This means improved oxygen intake and a boost in horsepower. But don’t assume that long tube headers always outperform shorty headers. It’s not that simple. Horsepower and torque output depends on the RPM range.
Factory headers, or “manifolds” are generally designed to meet the most strict emissions requirements, and be cost effective to mass produce. These manifolds are generally cast, leaving inconsistent imperfections within the inner ports. These imperfections can restrict the flow decreasing the efficiency of the engine’s exhaust flow. Their port design is typically geared towards quiet engine operation. In addition, they weigh significantly more than an aftermarket header.
However, on high-performance cars, like the Challenger R/T or SRT, manufacturers use short tube headers, or “shorties” (see photo, below). They are a great option to produce more low to mid- range power in reference to your engine’s rpm band. Shorties do a good job of emptying the cylinder of exhaust. This is especially beneficial on a big motor, like a Hemi, that produces large amounts of exhaust discharge. They, however, do not offer much ram aid, like long tubes, because they don't generate very strong negative pressure waves. Short tubes use welded mandrel bent pipes, rather than a casting. They are typically easier to install compared to long tube headers and accommodate factory catalytic converters. For emissions controlled states, short tubes are typically the only legal option.
Long tube headers are a great option for engines that build a ton of power in the mid to high rpm range. Due to their longer and narrower primary tube lengths, they require extra room inside the engine compartment. This makes them more difficult to install and may call for some costly reconfiguration (see photos, below).
Long tubes are a great option for someone who is racing and pushing their car to the redline. The goal is to produce maximum peak horsepower without worrying about things like catalytic converters and complying with emissions standards. Long tubes, however, will cause a check engine light on most modern applications, unless a custom tune is used to tune out the secondary oxygen sensors.
Long tubes keep exhaust gasses separate from each cylinder for a much longer period of time. Their length allows an elongated path for the gas to flow, thus allowing the gas to leave the cylinder with more speed because the gas has more time to gain velocity before it hits the collector.
Specifically, they work by creating a deep pressure depression that pulls really hard on the intake during overlap. This enhances the ramming of mixture into the cylinder. Getting more mixture into the engine with these reverse negative pressure waves is why long tube headers become increasingly effective as cam duration and overlap periods get longer. With a mild factory cam, where there is more dependence on efficient expelling of the exhaust than pressure wave utilization, there isn't a lot of difference between short and long tubes. It takes a decent cam, high compression and to some extent high RPMs to really get what long tube headers can deliver. The back side is they can over-scavenge the cylinder which will require enriching the mixture.
Here are photos of the modern Hemi engines with their “shorty” clam shell exhaust headers.
For racers interested in installing long tube headers, proven and trusted brand names are recommended, like: Gibson Headers, Kooks Headers, Hedman Headders, Hooker Headers, Pacesetter Headers and BBK Headers.
Also, to prevent corrosion, you should consider stainless steel or ceramic-coated headers. Ceramic headers are preferable because they run much cooler than stainless steel headers (258 degrees Fahrenheit vs. 870 degrees Fahrenheit) and maintain their out-of-the-box chrome-like appearance forever.