I built my own and used cone engineering for my parts, they have info on how to size and tune a merge collector. When I ran my headers, the results were "interesting".
Just got off the phone with Cone eng, parts on the way. Also Jericho GTX has a set of individual cylinder flanges with stubs, which I have my name on. The fact that I can build the headers and leave two or three tubes bolted up while I work ought to help welding time a bunch. R The plan is ;. 10 inch 1st step of 2 1/8 16 Ga, 14 inch 2 1/4 for second step, over all 10 inch of collector with a 3 1/2 inch merge, to 3 to 4 inch cone. Joe, what was "interesting" about the results?
