The main physical difference between short (“shorty”) and long tube headers is the length of the exhaust port pipes. With a shorty, port pipes merge into a single exhaust pipe within a short distance from the engine exhaust ports, while long tube header port pipes merge farther out. There are also performance, installation and legal differences between the two.
The different merge points for the two types of headers result in performance variations because the merge point directly affects back pressure in the intake-exhaust system. Back pressure from exhaust gases reduces the ability of the engine to take in fresh oxygen, which limits engine horsepower and torque. Consequently, the farther out the merge point of the pipes, the lower the back pressure, the greater the oxygen intake and the greater the resultant horsepower, which gives significant power advantage to the long tube style. That said, according to Autoanything.com, some enthusiasts contend that short-tube headers actually outperform long-tubes at generating horsepower and torque when RPMs range from idle to mid-level, but other factors such as tube diameter and engine size must also be considered. Beyond the mid-RPM range, long tube headers consistently outperform the short-tube style.
Short tubes have two clear advantages over long tubes, according to hotrodders.com. First, the shorty is almost always easier to install because it requires considerably less room than a long tube. Accommodating the extra length and shape of long tubes often means spending money to reconfigure the engine compartment and/or components. Second, the shorty is usually street-legal out of the box, while differences in emissions standards can render the long tube header illegal in some locations. (Beware if the header package is labelled “For off-road purposes only”).