for a collector to work right, the primaries need to be arranged in the firing order so you have a pulse sequence going in a continuous circle pattern. The primaries also need to be equal length and diameter so the timing of the pulses is even at the collector. I would also make a tall cone or pyramid in the middle to take up the "unnecessary" space in the middle of the collector, to reduce turbulence and increase the scavenging effect.
I'm no expert in our inline sixes, but it appears that our engines have firing orders arranged in two separate groups: the front 3 cylinders and the rear 3 cylinders. Makes exhaust design easier when you can treat the engine as two 3-cylinder engines and all 3 cyls are adjacent to each other. It would be more challenging to build a header if you had to combine cylinders 1-3-5 into one collector and 2-4-6 into another.
Because of this 3+3 design you could probably have true dual pipes working just fine. But once you get to the first pair of collectors and get two pipes out, proper secondary pipe lengths before the last collector could probably offer you a second scavenging boost for all 6 cylinders.
Last edited by 70Nova; 10/19/14 10:03 PM.
