[Alan Roehrich]

Absolutely equal length is not nearly so important as the correct size, correct length (there's a tuned length range), and smooth bends, with no unnecessary bends.

Yes, the tuned and equal lengths are very important, even though in Stock you often have a dual plane intake that does not have equal length runners.

In other words, there's a correct tuned length for the primaries and the collectors. If the correct length for the primaries is 32", you need to be within 1"-2" either way, the closer the better. But you should not add several bends, especially sharp bends, to get there.

If you stray too far from the correct length, for either the primaries or collectors, you can kill a significant amount of HP and torque. A lot of collectors are way off in length, and really hurt HP. If you need a 14" collector, and you have an 8" collector, it can make a serious difference.

The correct diameter is very important as well, although not quite as important as length. If the primaries are too big, you can often crutch them with a good merge collector that has the right length and has the right venturi size and shape to make up for the problem with the primaries.