Which are the best? long,mid or short? whatd the gains from each of them?

 

Really the gains are in torque. The longer the tubes, the more low end torque you're going to get. They'll all make around the same HP (providing you have all of them matched to a good Y-pipe). I'm an advocate of "do it right the first time" and thus I will always suggest getting tuned long tubes.

 

You can think of headers as a musical instrument in the brass section. The loudness of the instrument equates to horse power, the pitch of the instrument equates to torque. A tuba has a very long amount of plumbing which results in a low pitch (low end torque), a trumpet, on the other hand, has short plumbing which results in a high pitch (top end torque). Since both instruments can be equally as loud the horsepower is pretty much the same, which in engine terms it means exactly what 95slvrZ28 said. The length of the tubes, as long as the diameter is correct for the size of the engine, has little effect on power output, but has a big effect on where the torque peak occurs. For a pure racing engine where RPM are kept up at all times it is advantageous to have short tubes, but for a street engine not capable of very high RPM and moving a fairly heavy car, long tubes would be best, if nothing else to get the car movingoff quickly.

 

I really think it depends on the build of the engine also. On of the main advantages of headers is the scavenaging ability they will actually pull exhaust gases away from the exhaust port using the pulse of the other exhausted cylinders at higher rpms. I dont think you would see a big difference in a stock engine but I do think you would see broader hp and torque curves with a proper long tube header and a longer duration cam. I have a set of flowtech afterburners long tube on our car no exhaust they have smaller primary tubes and a different pipe configuration that supposedly aids in the scavenaging. I am going to try and put some header extenders on to see if it makes any difference.

 

I always knew that for steet engines long headers are the best.