Here is a technical explanation of the advantages of shortie vs. long tube headers: This is, basically, a question of exhaust gas scavenging efficiency. Effective scavenging is an extremely important factor to consider in maximizing your engine's volumetric efficiency, or "V.E." Long tube headers are headers where your primary tubes are on average, at least 28" in length and are much more narrow that their short tube counter parts (like the ones on SRTs). These type of headers, generally speaking, are best when used on a street rod, or "smoke show" application. Basically, lighting up the tires from stoplight to stoplight, generally with a mid to low power band. This is because of the way the engine breathes at mid and lower RPM's. At the low to mid end, the best way to maximize your scavenging effect, thus helping to maximize your engine's V.E., is to move the exhuast out of the engine as fast as possible, or with as much velocity as possible. Long tubes work best for this because of their length, and their width (well, lack of width). 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. Now, you've heard car enthusiasts state that any restriction is bad for a motor, no matter what. This is not completly true, especially for our Hemi engines. Small strategically placed, smooth mandrel restrictions can be a good thing due to the fact that well- placed, correct-sized restrictions followed by larger openings actually speed up exhuast gas flow. So the smaller diameter tubes actually scavenge better in the mid and low ranges. Mid and low ranges don't produce a lot of actual exhaust volume, so small tubes don't restrict or "back up" flow. Large, short tube headers make for "lazy" exhaust gas speed when exhaust volume is low (as it is in the low and mid range). However, if you don't even begin to tip into your power band until about 3,700 rpm, you may consider short tubes. High rpm operation in a big motor (not talking about 4 bangers here), yield large amounts of exhuast gas discharge. This is where you need the larger diameter tubes, to get more volume out of the cylinder. This is where you can lose power due to pumping losses on the exhaust stroke. In an ideal world, your exhaust system would be so effective, that by the time that piston starts coming up on the exhaust stroke, your ports and headers will have scavenged all exhuast gas out of the cylinder during the duration of the exhaust pulse. If there's no sizable amount to push out, a low pressure area in the cylinder is created (also known as vacuum), almost causing a "pulling up" affect on the piston. So, your not losing power by pushing, you're gaining power by being pulled.
