Has anyone ported stock magnum heads and have the before and after flow numbers .???

Brooks James said

540 hp, so..IIRC the basic calculation would Be 270 CFM x2 = capability of 540 hp

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Look at CFM/CID. Just because you have 270 CFM doesn’t guarantee you 540 HP. Especially on pump gas with the de facto way too low pump gas compression ratios.