Thread: 302 cyl head print (needed!)

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From my discussions with the custom header guys and my experience on one set of headers, the flanges you buy have the ports sized to match the OD of your prescribed primary tube. For a 302 the "normal" is 1 5/8" primaries and the tubing is a controlled OD which gives you a circumfurence of 5.11" so the port perimeter will be about 5.15" or so. When you form your tube to fit and tap it into place you'll get nearly a zero gap fit. Header guys I talked to said to weld on the outside, leaving the machined surface of the header flange unmolested, but to never weld both sides of the flange.

Sounds like you already know exactly what you want to do, and that you either own or have access to some pretty sophisticated equipment. Not many people can afford to spend time making things like custom header flanges and make it pay off so you are in an enviable position. Good luck with your header build. I'd love to see pictures of your process as you move forward.