Ok that sound about right, anyone else with something to add about this topic?
Only that CNC-ported heads are digitized for a computer controller from a hand-ported head.
This has a few benefits and at least one possible negative.
First benefit is that only one nearly perfect hand-ported port must be done. If we *assume* it was done really well, then (benefit #2) all of them will be equally good. Also, CNC port programs can then be modified to cut test ports much faster and more accurately than hand ports, with very specific changes for additional testing and improvements.
The first negative is that all the ports are identical - generally thought a pure benefit. The issue is that flows are not the same between the end and center ports, nor front to rear, and where experience and skill come into play. However, the ability to make the same port, but with changes just for a specific location is nearly impossible in the real world for most.
If given a choice for hobby and semi-pro level engines, it seems that starting with all ports the same (identical with CNC) is most productive, if they are then modified for individual flow as-required. I know there area high-end heads out there that are fully CNC, but each port is not
the same, adn the pro teams pay big for them.
Hope that makes sense.