Modifying And Welding a Cast iron head

bOb shingler said

i think it would be better with rectangular tube pressed in because they flow much better but then again it's hard to drill one of those holes.

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i would think a round tube would flow better for a given port area due to no edges for turbulence??

but it would be another good test!

do they make any rectangle tubing with "soft" corners or would i have to just use normal rectangle tubing and weld/smooth the corners??