My grandson, son and I are busy building a lakes style header for the big Pontiac motor we have in the 1926 T Touring rod we are finally (I started gathering parts in North Dakota in 1974) building! Its a great project but there is a lot we don't know about the specifics of making headers. For example, how best to mark and cut the shape where the tube from the exhaust port will join the megaphone? It is a real challenge. Any one know of a good video or tutorial on this? Luckily my grandson is a certified welder and we have a great shop. Thanks as always for any advice you can share. Michael
I'm guessing you want to make a curved transition from the header flange to the cone like the rear exhaust port. You will basically need to have a section of pre curved pipe and slowly shape and fit it to the cone, it will take a little extra time instead of just running a straight shot from the flange like Sanderson headers does. You will be getting in touch with your artistic side here, it will require patience and a dremel type tool. Once you have the small tube fitting up with the cone, you can trace the outline of the small tube onto the cone and open up those holes the same way, a hole saw will work for the initial hole but since it wont be round you will need to bust out the dremel again to port match it. Don't be in a rush to get this done, like I said it will take a fair amount of time if you want a nice result. Also when building headers from scratch it is much better to tack everything together so it can be broken down easier if needed, no final welds until you are happy with the shape. You guys aren't too far along to cut it apart now and just dress all of the joints and just tack it all back together. It will be easier to shape the holes in the cones without the flange in the way. The header should only be on the engine for fitting up things as you go, most of the work will be on the bench.
I think if you search duck bill and header , or fish mouthed that might help? It’s a difficult thing to do and you gotta just sneak up on it but hopefully that term brings up more results
Typically for what I call a Bologna fit being a flowing angle onto a radius I will sacrifice a section of a bend and using my Wiss hand snips going very slow hand cut a piece that fits the way I want it to. Once I like that I then trace that profile on the collector to cut the hole. Always undersize that hole and hand file to fit right. Then transferee to the actual part I'm going to weld in place. It's a very slow go process to get a good tight fit for a small clean weld joint. Hand snips and a bench grinder are a must have tools for me. I'm sure in production parts it's done on a C-n-C machine but for one off at home you just have to work your way through it.
Michael, on the bottom of this page, it shows how I do this style of header. Hope it helps. https://www.jalopyjournal.com/forum/threads/10-track-roadster-build-marty-strode.1181804/page-10
There are a few ways to accomplish, You can use straight tubing draw out radius angle cuts , making a circle . (( witch will be alot of welding & grinding to make smooth radius finish)) Or J's pipe Or fabrication Donuts for tight radiuses .
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