Hi-po Exhaust manifolds

1970Duster said
Just a thought/question have any of you ever tried to improve the flow of the hi-po manifolds? I mean like grind away all the bumps inside of it (as far as possible anyway) and smooth it all out? I know it won't match the flow of headers but it would improve it right.
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Several years ago I sent my 69' RoadRunner 383 exhaust manifolds out to extrude hone and it definatley improved the flow. They basically mix media with clay and force it through under pressure.