I've had a fair amount of CNC heads on the dyno and lots of them run really strong. Some CNC work is so good when it comes off the machine you really don't want to touch it.

Chapman is one of the guys who figured this stuff out 20 years ago. If you go dig around the internet looking for articles on Chapman you'll find a bunch of cool stuff. He was using CNC porting to win NASCAR races 15 years ago. I think he was one of the first guys to get raw castings from the head mfgs and then machine the entire port. I don't think they did much if any hand finish work on Chapman heads.

Alot of varied opinions here, good pints in all. Im not sure if there is a right or wrong answer all things considered.

In the pulling world here is a neat head if you got deep deep pockets.

I recall 1n 79-80 when this started it was just a block of al. and a old bridgeport. At the time it was just a few hours a day between jobs and didnt seem that big of a deal or project, but it was.


This head is said to go over 500 cfm and then add two big turbos....I dont think a head like this would need any cleanup work.

I know if I live long enough and keep testing I will find a CNC'd head that acts and runs the way it should. No such luck yet and my Friend was really disappointed in his CNC'd AFR220's but we got them calmed down and his small block chevy truck cranked out a 10.40 two weeks ago.

My cousins built John Deer pulling tractors years ago, they built a dual overhead cam cross flow head for one. Then NTPA outlawed it after one season, said it wasn't a production piece as JD at the time wasn't a cross flow head. Heck I didn't think the three to five turbos were production either.

You must not have read my post earlier in this thread, John.

Guy who bought my old car with W5 motor. Heads were fully hand ported by a small block Mopar head porter to the Max. I ran them a few years, new owner ran them several years.
They were obviously thin, and finally started leaking water and became unusable.
He had the motor freshened up while the old heads were still on it, and had it dyno'ed and he raced it...... Heads went bad, he bought new w5 heads, had Modern CNC them( I believe the program was based on the hand port by the same guy).
Anyhow put new heads on same motor, takes it to same dyno, takes it to same track.
Bearing in mind the CNC was kept " small" because of known W5 core shift, the motor lost about 20 horse and a tenth at the track...... So very, very little..... And considering the heads now have integrity, I would rather have them than the original, thin hand ported units.
the above is dyno and track tested proof of excellent CNC results. So there are good programs out there.

As I said I've never flow tested a CNC'd head yet that did not go turbulent.

Because its a mass production of a poor design, or because the mass production type of CNC porting leaves a surface finish more likely to have problems that cause that turbulence?