Technical I have a question about the flange when building headers

some simple (yeah right) headers I built for a certain little "race car"
with the exception of individual flanges cut from 3/8" plate, these were built as described above,
they are all tied together with a support hidden under the car.

 

more, just 'cause

reversed Belond:

 

and
store bought 3/8" flanges, tubes fabbed from mandrel bends..

 

If it's going to a solid header once done, flat flange, split it between the cylinders, let it eat. Some don't like split or separate flanges but it lets things move as they will on a street car and usually never leak. And I concur, store bought production headers usually leak as though it's a requirement. Cutting the flanges was a pretty reliable fix.