There is so much that goes into the design of headers that the lines have essentially blurred these days, in the old days the shorter primary tubes usually built better mid range power than long tubes of similar size did. However, open up the long tubes to a larger pipe and they make much better power in all speed ranges. But it isn't just primary tube length that you have to deal with, don't forget the collectors, both length and diameter, and even the design of the innards of the collector as well. Do you add a subsonic diffuser or not? If so you effectively extend the length of the primary tubes, but still get the advantages of a longer collector.
... and what design header are you talking about when talking long tubes? a 4 to 1 header, or a tri-y design?
In the end on the street these days the difference isn't enough to worry about what design you choose, as long as you are going with a quality header design.
Originally Posted by Dreadful_Knight
Well, sounds like the consensus is LT's. Does anyone have any dyno runs or any info to back up these statements? Not that I don't trust you guys here at TCCOA, you've never led me wrong, I just like to have some info to throw out when someone tries to debate with me.
One more question, what size primary/collector is an ideal combo for N/A 5.0 h/c/i for LT's?
The problem with dyno runs is that you don't know what tune people are using on their engines to get the numbers. You can duplicate the parts build up, but if you don't tune the engine the same way it was on the dyno, you won't get the same numbers.
As to what primary tube size and length, and what collector size and length, that will vary depending on what the engine is going to be used for, and what displacement you are running, and how much airflow you are getting through the engine. For the most part a 1 1/2" or 1 5/8" tube about 31 inches in length, with a 3 inch collector that is about 6 inches long does quite well for the street on all but the smallest and largest engines, and for engines making less than about 450hp on the motor.