I am running them port to collector freehand using the routing I designed and will see where they end up for length. I have not built a set of 180's before or measured a existing set so Im not sure where the dimensions will fall.
I know the currently available undercar headers for a Pantera feature unequal and very short primaries. I am hoping to be able to gain some length with this design.
When my car is done I will chassis dyno it and then have a real number to reference if I need to make a header change. I am not trying to make these equal length because I do not know what length the engine needs. This will be accomplished by the chassis dyno testing.I also do not know how a 180 is affected by a unequal primary. My goal is to keep the discrepancy minimal (less than 8 inches)given the design and the room I am working in. *End of Edit*
I start by mounting a header flange to another 400 I have in the shop. I am not using starter stubs because of the lack of room between the header and the car. I run the number 1 pipe back to the general direction it needs to go. I am using a metal strap to locate the end of the tube so that I don’t run it too low. The Right hand bank cyl’s 1-4 will be the bottom tube set. The LH bank cyl’s 5-8 will be the upper tube set. In order to keep the primary pipes and flanges one piece from side to side I am going to construct them in this overlapping fashion.
I do the same for cyl #2
And #3
I then mount the flange and pipes into the car. I remove the #3 tube to have better access to run the #1 and #2 tubes.
I run the #1 tube first. Where cyl #1 is the furthest away from the collector I run it to the closest collector opening.
I run cyl#2 to the closest opening in the other collector. Since this side of the engine will be the lower bank of tubes I angle the pipe downward as it exits the collector. I need to give myself plenty of room for the pipes that will go on top.
