415HP from 318ci IS POSSABLE!!

That makes sense at there is far more area under the curve with a roller cam. I recently read a dyno comparison between two cams with identical specs with one being a being a fast rate hyd flat tappet and the other a roller and the roller cam had significant gains all across the board.

How you get these numbers from such small valve heads is amazing. As you say, velocity is key but how you do it is a mystery to me. Port shape, transition into the valve seat and the shape of the underside of the valve are all I can think of. Do you use a pitot tube when porting?