I am building a set of headers for my 261 with 4 equal length 44" tubes into a 10" collector. I am thinking about the Siamesed ports. The firing on 4 and 5 is 240 degrees apart and on 2 and 3 120 degrees apart. I want the headers to scavenge properly and was thinking that if I use 1.625 pipes 1 and 6 and 1.75 pipes on the other two larger ports, the scavenging balance will be off. I'm thinking I should use 1.625 pipe on all ports with only a flare to accommodate the two larger ports. I think the firing and subsequent exhaust stroke on each siamese is far enough apart not to interfere with each other. Has anyone built tuned headers for a 235/261 and what did you experience?
Thanks
Warren
