The d16y8 is the best by the numbers go but is in a heavier body car. The ports aren't as much different as it is the combustion chambers. The z6 has a normal style combustion chamber while the y8 has a quench type combustion chamber The compression ratio between the two states obviously why the hp is different between the two. d16z6 cr 9.2:1, d16y8 cr9.6:1. Simply put the head on the d16y8 is the best of all the above. As far as cam profiles are concerned, It shouldn't matter. If you have the head off, you might as well pilddle with the head for a little while and change the cam. It is not hard to do. Cams can be changed much more easily than getting your head modified and much less expensive. Head design as a whole goes to the y8 no matter what head has any certain jdm cam. But it is not much of a difference. Just the way things are. 1.5 liters of displacement is not worthy of being praised and are worhtless other than to turbo. They are not even that great then with their tiny ass rods and ultra low displacement. If any d-series is being built for any kind of power, buy some rods. But there is something that you do have to do when installing a larger set of rods into a d-series. When building a d-series and installing the rods, they will not turn over and tey will bind on the bottom of the cylinder sleeve. There is not a chance in hell that this will not happen as when I had a d-series there was just too much to be filed out to just be bad luck. So if you want to go the d-series route, prepare for an expensive bottom end build(unless you and an engine builder friend from honda helps you like I had for free but if not be wary) at least on a y8. I think the blocks are identical between the z6 and y8 though.The reason it will be expensive is that you will have to keep taking the bottom end apart if you do not take enough metal out and it takes time because it is the pressed in iron you will be cutting for clearance. make sure you have something soft on the end of your file so as not to damage the cylinder walls. I got carried away in typing, sorry.