CNC Mill Mark Removal in Intake Port

If some of you guys would pick
Up a grinder and grind half as hard as so try to scientifically figure something out you could be rich. 30 plus years ago the experts said smooth exhaust and rough intake ports and it still works today.

Which way should my grinder rotate though, clockwise or anti-clockwise? Does it depend on which hemisphere I'm in? Shouldn't the bit be reversed when I reach in from the bowl side?

You're right, and the experts landed on rough largely by applying the science above which was sussed out back in the 30's, 40's and 50's.