Since you don't see this kind of stuff posted too much I figured I'd show what a full race ported GN1-R head (out the box) looks like when compared to stock iron heads. This gives people an idea of how much larger aftermarket heads are. I ported the stock iron head you see myself and has been a best of 6.53 at 107 in the 8th mile. Also to note, my "R" heads are not the tall port offered by Champion. There's at least 3/16" or more to make the port taller. I'm sure all the really fast guys have MUCH larger re-worked heads than these.