Dynamic Compression Ratio

:scratch: I'm putting together my 340\373 engine and I'm at the point of buying a cam. I measured all the volumes and the static ratio is 8.74 to 1. When I add the rod and cam closing point I get the dynamic ratio at 8.14 to 1. Is the dynamic close to what it should be for a street car? I looked online and everything I read says you don't go over 8.2 to 1 on the dynamic for a street driven car. Why does Keith Blacks compression calculator tell you to add 15 degrees to your intake closing point and others online don't? Makes a big differance in yor dynamic ratio. Can someone enlighten me. Thanks, Bob