Question about the rotor it self, it ranges from 8.5-9.7 on the Rx7's My question is that is 8.5 a deeper grove(hole) in the rotor or is 9.7......i read that the R26B used compression "10" rotors ....also which is the best for N/A power and if the deeper grove is better then ill be Grinding away

lower compression has the lower dish.

which way is lower 8.5 or 9.5

8.5. That means it will compress the volume of air 8.5 times the original volume, whereas the 9.5 will do it 9.5 times, hence the higher compression.