As has been stated, the SE 255 cams are not for high compression pistons. As you can see in my signature I am running the SE259e cams and 10.5:1 pistons. My CCP is 180 and even though I have installed MCR's, I have not used them in over 10K miles on this build. Choosing the right cams and compression is key to a good build. I just ran over 7500 miles and most of that was out west using 91 octane, in high elevations. Never experienced any engine knock the whole trip, in fact have never had engine ping, not once with this build. Good luck on your choices.