MBDiagMan

It doesn't matter if the engine is stone stock or an all out stroker that'll take the car into the nines. In either case the improvement when switching from shorties, to FULL LENGTH headers is dramatic as mods go. Shorties are nothing more than free flowing manifolds,

The only difference that should be considered as to whether the engine is mild or wild is the tube size and length. To fully understand all this, you really need to take a course in fluid dynamics, but basically:

For a mild engine, use small diameter tube so that the gases travel further down the tube as it fills. This produces gas speed which draws out more gas as the exhaust valve is closing. This is called scavenging. For a larger engines with higher RPM power desired, use larger tubing so that the tube doesn't fill up with gas before the exhaust valve is closed which will kill the scavenging effect.

The second effect if you are "tuning" the header size is tube length. There again the tubing length will determine when the pipe is full not being able to take in any more gas as the exhaust valve closes. The other effect of the tubing length is sort of like tuning an organ pipe. The length determines the frequency. This parameter is more important for a high RPM engine with a narrow power band. In that case you can use the pipe length to enhance the power slightly at a narrow RPM band.

For a street car, you can just forget about getting precise tubing length and just go with 1 1/2", full length headers and you will have an increase in power from off idle all the way until you get to rod breaking engine speed. In fact if you use large tubes, there won't be a lot of difference between them and small tubes, but either one of them will be a DRASTIC improvement over shorties.

The REAL difference when comparing headers is comparing shorties to full length. Again the shorties or nothing more than free flowing exhaust manifolds and will help SLIGHTLY over factory manifolds. Full length headers of almost any size and length tubes will offer a DRAMATIC power gain at all engine speeds.

That's the "long and short" of the subject.

wrenchturner75

or another option is to use a stepped header which is the best of both worlds for a street car, every so many inches the tubing size is increased, this allows low end power and also gives the top end power, but they tend to come at a hefty price, but nobody ever told me that hp was cheap, point is they work extremely well.