Originally Posted by dorko
hx is a more economical/environment friendly version of the ex...so i doubt it will produce more HP either way you look at it
huge thread on this on honda-tech. y5 head is a much better designed head, and could possibly have serious potential BUT - there is no real aftermarket support for it, and all the potential it has will probably stay untapped, unless the goal is GAS MILEAGE. Stick with the y8 head.