ford saids that you hone each cylinder for 45 minutes. with any grit as long as it is 45 degrees.45 forn45.on my 302 i used gapless rings with no problems but on my 428 used regular cast iron rings with no prolem. but i do not run nox don't beleive in it. the 302 was 12.5 to 1 and the 428 was 11.5 to 1.