My thought is there is no difference between CNC Ports versus Hand Ports. The bad part about hand porting is duplicating all the other holes. This took me about two weeks--not two days. As Mr. P Body states, having a good master is the key. If you copy a bad port, you wind up with a bad port. By hand porting, once you have a good intake and exhaust port, you have to humanly duplicate it by measuring; which is extremely difficult and very time consuming.