Hi Panic, that is my blog. I noticed that you had left a couple comments, and I appreciate it. In that particular computation what I meant to say was that if each valve (intake and exhaust) were sunk .050" it would total the 4.39cc. I used 1.940 and 1.750 as my valve sizes, so the math does work out. I should have made it clear that I meant both valves were sunk.