CNC'd ported vs hand ported heads: Discussion, long post

Just thinking today while sitting at my porting table. After I have one port finished and off multiple trips to my flowbench its time to crank up the stereo with some Stevey Ray Von, Doors, or some other favorite CD and start the usually 2 day process of finishing the other ports. At these times ones mind tends to wonder. Now for the discussion. I personally have been able to pick up a minimum 15cfm and as much as 30 plus cfm on CNC'd heads. I've had guys bring there heads in for flow testing after their car hasn't performed anywhere near what they were told the heads are capable of flowing and the numbers aren't even close to what they were told. Several years ago I would have said CNC is the future of our sport but if the hand ported head isn't a GOOD blueprint, now what? Hand porting is becoming a lost art with many of the true blue teachers passing away and few are interested in pursuing it for full time work. My Son for example has no interest in giving it a try and I even paid for him to go to Darrin Morgans 2 day theory class. Look at Edelbrock for example trying to release a new head and all the issues they are having. I personally see performance issues taking a step back in 10-15 years. What are your thoughts?

CNC will never replace hand porting for getting to most out of a set of heads. I like It for the fact that you can get alot of the material out of the way easily and then finish the ports off by hand and save some time. There are definately going to be less people who are good at it, but as long as there are people who want the most out of there heads and are willing to pay there will people doing it by hand.

This is coming into a lot of different areas... fab work
is going down hill.... hand porting is also... the big
thing with CNC is you have to have a master to scan from
so if no one whats to get dirty anymore... its hard to
get a good master... at least I still see a few people
that are still willing to try to build headers... hell
I offered 2 different guys on how to build headers...
neither wanted to even try... that went right along with
building complete exhaust for cars or cycles... that was
the reason I sold all my chassis bending equipment... no
one wants to work

been fighting the CNC crap for a long time. One company ( a big name head company) called me a crook and a liar because their heads were CNC ported and didn't flow any where near what they said. The ports were so turbulent you couldn't read the manometers.

Then the customer is pissed because they paid for CNC and the big name companies tell them not to finish the ports by hand. I have NEVER seen a port that was CNC finished that didn't improve with hand finishing.

In 10 years I'll probably be dead and so will performance automotive stuff. It's got one foot in the grave and another on a banana peel right now. If a kid is under 15 right now, they will NEVER understand performance cars. Ever. They are indoctrinated from day one in school (and every day on TV, in the papers and on the web) to hate cars. I was born in the wrong generation for sure.

The heads you ported for me performed better than some big $$$ heads I paid for. Don't give up just yet, there are some young un's that would like to learn.

Maybe true BUT some of the GOOD cnc stuff is profiled AFTER a bad ass port is achieved so it does have it`s place but too many lies follow and the #`s don`t line up as stated........Oh, my heads were hand ported by me and approved by Ed Mosler fwiw.

My Eddy's were ported By Jeff at MCH and I think they move pretty good for what I do. Is there more in them? not sure

I'm sure there have to be some good CNC'd stuff out there but honestly I have been really disappointed with the ones I've tested.

With modern computer flow simulations you should have a good idea what a cnc port will do before the head is ever ported. It is the future, because there are places that will teach you how to do this.

Trying to learn the art of hand porting from someone is like trying to get the chicken recipe from KFC.

I'll believe it when I see it.

The numbers for computer simulation must have meaning or everything you do with them is WORTHLESS.

A rudimentary understanding of such things as laminar flow, Reynolds numbers and a bunch of other stuff is required or what you design is junk.

There are many "rules of thumb" I use that still work to this day...I suppose you could program those into simulation programs.


But herein lies the crux of the matter. Today's generation think the computer has revolutionized the world, that we are doing things now that have never been done and that is 100% arrogant horsecrap. Go find an early Oakland engine and look at what those engineers did WITHOUT CNC. And, evidently, we have forgotten/ignored or are ignorant of what was accomplished by THIS country WITHOUT computers during WWI and WWII.

All CNC means to me is that whatever you have that is CNC'd will be almost exactly alike, warts and all. The tool path is copied exactly the same, every time, even if there is no material there, or there is more metal there and you have tool deflection. All errors are copied as well.

As I see it, the public is getting screwed with CNC porting. By the time you fix the CNC work, you have the same money in the heads as you would if they were hand ported. And this is why the big companies tell you to leave them as is, they can't sell you a semi-finished head for retail.

There are exceptions to this rule, but the rule is correct none the less.

John...I am quite happy with my hand ported Victors. Radar Lechtenberg did them along with matching the Indy intake. He learned the trade in the late 70s from Gary Ostrich. Worked for him a while before setting out on his own. He used to do a lot of Top Fuel stuff till it got to be too much work for him. Radar is still doing cylinder heads but he is getting up there in years and has slowed down a bit. The guy does a heckuva job and I am proud to have a set done by him!

And this too is a big part of the puzzle. PORTED INTAKE MANIFOLDS. I ported a set of Chevy Dart Platinum's for a Friend that started out flowing 260 then backed up from high air-speed. When I finished porting them they were flowing 315-320 so we bolted his stock Victor Jr on them and they were now flowing 260 cfm. He was flabbergasted and said we didn't gain anything but I then said to him, what do you think they were flowing with the intake bolted on before the porting work. I charged him another 200 dollars as he NOW wanted the intake ported to match the heads but not before he spent another 400 dollars to buy a Dart intake and it was just as bad as the Victor Jr. 6 months later he dragged over the Dart intake to have ported. LOL

The computer HAS revolutionized the world, for good or bad is the opinion of the person. Most older generations would say bad. Most things that have been accomplished in the past could of been aided by a computer for a quicker POSSIBLY better outcome. One of the greatest accomplishments of WW2 involved a different country, creating and using a computer.

We might not be at the point that CNC programs and simulations come close to what a hand porter can accomplish but we will one day as long as there is money to be made.

It is all just a matter of economics. If the sales volume justifies it then there is no reason that a CNC port can't be just as good as the best hand port. All it takes is time and money to duplicate the ports.

I thought the essence of a CNC port was really so you could essentially purchase a slightly more economically priced mass produced ported head based on an intricately digitally mapped and 'science out' hand ported (and flowed) model. To think the CNC would be 'better' than the hand ported model it was based on would be a stretch, I thought cnc was just applying modern mass production technology to a hand science as a means of keeping the unit cost and lead times down. I would think hand finishing a CNC set would be beneficial in terms of ultimate bench flow numbers but we're probably talking only 10ths of a percent impovements overall in practical terms. Ybut by hand porting above CNC you maybe pushing the safe limit envelope if the heads are nearly maxed to begin with.

But they aren't maxed out. Heck they weren't even thought out in my eyes if a head goes turbulent above .600 like most of them do. When air is traveling at 400 plus FPS across the whole short turn that port is BEGGING for more area which in turn will give you more flow.

Once someone has a good flowing hand ported set then its
the number of steps/transitions that is involved.. I had
a set of CNC heads done(W-9s) then had them flowed... then
I went over them with hand bits... it picked up 3 CFM on
the mid to full lift... same numbers down low.. but I will
say there was some big steps/transitions per step

The article HERE brings up some of what you're talking about, too.

I think you hit it there on the head, people want miracles. Say CNC they think 4 seconds faster. Your early duster ran fast but I bet it took awhile trying different combinations till it ran the fastest. Open up the heads to big flow, and the rest goes out the window, everything will be changed to work with that flow. Chrysler had those combinations pretty much figured out for us back then, we're on our own now and very few with the knowledge. In my business I spend almost as much time educating the customer as doing the work. To much misinformation everywhere.

Ive always thought as well that the mass produced heads got the cnc job because it was a mass produced. Ive never seen a head not respond to hand porting/blending as the finishing touch.

If one knows the casting well they can go past the so called safe limit that the mass produced cnc head.

With cnc becoming more the norm then not what about the motorsports that dont have cnc programs such as tractor pulling. Ive done many cast iron inline six heads that there will never be a cnc program.

As well as alot of the basics of head porting can help alot of heads to a point without a max effort and big costs.

Intake porting I think goes hand in hand with a max effort head porting job, this intake here in the pic is more or less maxed out runner and port wise and took a good amount of time to get there.

I like having the whole motor present to get the dead on exact port/head match which takes a good bit of time for just that process.

That is a classic article. Anyone who wants to build a race engine should read that article a few times.

I bet you could improve on most hand port jobs like that as well.

I think a lot of people think CNC heads are desighned on a computer, they are not (normally). They are a digital copy of someones hand port job, it will only be as good as the original hand ported head. I think a lot of CNC programs are too conservative to keep from cracking and such and speed up the process and keep people from sticking too much head on their engines sort of like how people put too big of a cam in most home built engines.

If some one made a real awesome port and had it digitized you could make CNC copys just as good. Most CNC heads just don't have that awesome of a port to copy.

Wish I could have gone to one of those classes. Looks like he stopped doing them after going back to R-M full time.

I'm just doing stuff like this in my spare time for fun(?). Not sure how long I could take it as a regular day job.

A cnc machine knows nothing by itself. If the cnc port doesnt move air then the digitized hand port lacked talent. And tool deflection? Really? Even if it pushed .010 it would still be a better REPEAT than a hand port.

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.

I have flowed many cnc ported heads. AFR heads seem to be right on the money with my bench. All others have fell short. As cast heads usually flow really close to advertised though. It seems to me that the superflow 1200 puts out higher numbers. Maybe it is actually more accurate though and my bench is just reading low compared to big box stores with mack daddy flow benches.

I really dont know what you guys mean by hand finishing a CNC port. I usually find no difference in flow sand rolling a port so mine are left like Brads picture above.

Btw, nice work Brad

I know of a small block engine that had its heads hand ported.
After they started leaking water, they were scrapped, the same model/ type of heads were given a CNC port copied from the same guy who had hand ported the original set..... In other words his program/ parameters were used
The results thus far..... Based on both sets of heads being on the identical engine and dyno, , at the same track, in the same car with no changes other than literally the heads ...It appears there is about a 20 horsepower difference in favor of the hand ported heads...... That was the difference on the dyno...... It appears the track difference is a solid tenth...... The CNC heads are without a doubt " smaller"..... But have more integrity regards the possibility of leaking.
This on a 700 ish horsepower engine

I will dig up some pics on my work computer late tonight of a cnc port before and after. For example as cnc programs vary and ive seen areas like where the bowl/runner meet that fair better with a cleanup and removing a bit of material. I myself never sand roll anything, just use a finer cutter in a die grinder and like that finish.

Also with the limited heads for small blocks to increase port volume and csa using a cnc head as a start helps since most are done in so called 'stages'.

Sounds like that small block wants a bigger set of heads

I know what your saying, i have a set of west coast cylinder heads "stage two" in my garage right now.

Yep.... The bane of 59 degree Mopar stuff since guys started offering long armed cranks.Huge cubic inch potential, but small 30+ year old heads designed to be used on sub 400 inch stuff at most. Big drink, small straw.

But worth the time. That is why everyone with a grinder can't port heads. Very tedious time consuming work.

Me too! I had Radar do my 440-1s, and recommend a cam. First time out, 8.96 at 3,000 lbs, 528 cubes.

l deflection IS an issue and depends on several factors. I wouldn't [censored] about .010.

If you can't match CNC heads by hand for repeatability you need a better porter.

I hand port to suit the combination, CNC can't do this, knowledge is power

I hand port because I can't afford to send my heads to anybody that knows what they are doing. LOL My hats off to all the professional porters out there. My cast iron heads took F O R E V E R to port to my satisfaction.

I will never claim to be a professional but I do enjoy doing it most of the time. I would never want to do it for a full time living. Just finished my Indy's at 11 pm tonight. Will do the final valve job and deck cleaning tomorrow and hopefully on the engine ready to go in sometime tomorrow. Who knows maybe some passes this weekend

Looking good!

. Thanks. Can't wait to give them a try

I think the real advantage to CNC ported heads lies in the ability to model the heads and design them using CAD. You can model down to the finest details and repeat those details in every port. The top CNC shops are doing their design work in CAD and CNCing them.

Not sure what to make of this thread. Is the art of porting mainly based on some individual personal theories, with a prodigious amount of try and error on a flow bench? What happens when flow changes go down instead of up? If the art is slowly dying off, because of time and CNC, seems like the time for a well researched jointly written book, with chapters by each of the prominent willing head porters. Seems like the book would be able to be well priced if the secrets are shared by those in the twilight of their profession. The attraction to me would be reading all the different views, one, not so much.

Head porting will never be a fits all for each build like a cnc head forces on you. When sitting down with a customer with hand porting you can shape the port to work for different builds. Play with a head on the flowbench that was prepped for a stock class car and you will be amazed.

I can tell you there is more to head work than flow numbers. The shape of the curve, how the head responds to pressure changes, how the port does in direction changes......just to name a few.

I have done heads that flowed LESS when I was done that went faster. The port had issues. But because the original head guy was into big flow numbers he missed an important detail.

I also love to kill "low" lift flow. If you think about it for a bit it will make sense.

I'd write a book, but would you pay to read it??????????????

[quote=pittsburghracer]Head porting will never be a fits all for each build like a cnc head forces on you. When sitting down with a customer with hand porting you can shape the port to work for different builds. Play with a head on the flowbench that was prepped for a stock class car and you will be amazed. [/quot




^^^^^^^^^^^^^^^^THIS^^^^^^^^^^^^^^^^^^^^^

Good CNC shops can size the shape of the port based on engine design in the modeling software.

Check out Curtis Boggs Race Flow Developments web site or Facebook. I'm usually at his shop a few times a weeks and see this all the time.

Curtis will usually CNC port one off heads as well

I have always felt any CNC port job should always be finalized with hand porting as to me the CNC gets the basic job but will never be as good as when finished with a pro's final hand porting. Now I thought if a good head porter has a CNC machine and can put his good port prgram in it then it would save the porter alot of work by doing most of the work and then the porter can finish them up to be just right. It would save the porter alot of time and work so he only has to finish the job up and put the final touches on it.
I bought my heads from Dwayne Porter and he did some porting on them but not a ton of work and I was happy to have him port them as I feel he is one of if not the best out there. But if he had a CNC machine and had it do most of the work where he just did the final touches I would not blame a person who does porting for a living to use the CNC machine as it would save them alot of time and as long as its there program and they finish the job to there specs then I can see why they would use it. Ron

CNC can do 95+% of the work in less than 5% of the time, allowing humans to do that last little bit(if it's worth it) and focus on important things like improving the entire system.

Do people actually enjoy the numb hands, sore backs, picking shards out of skin and hours and hours spent grinding out the bulk metal before you even get to the part that requires brainpower?

It's not one or the other; it's both focusing on what they're better suited to. S/F....Ken M

I just can't see paying twice to get it right. I could see if you got a GOOD cnc product but I've tested lots and they just aren't doing a very good job. They sure look pretty. A good Friend of mine challenged me to race my small tire car with his 20,000 dollar small block Ford with the pretty cnc heads and he can't even out-run my Edelbrock headed small block. LOL. He hasn't been quite so mouthy lately but I have a hard time keeping a straight face around him.

John, I have really enjoyed this thread. Takes me back probably 10 years ago. When RyanJ and Fast68Plymouth AKA Dwayne Porter and others head porters had regular discussions on here about their work. Sadly not much of this goes on here anymore. What a loss for the younger guys. Jim

Thanks Jim. It gets kinda stale around here sometimes so I thought this would kinda be different. I was hoping Brett would stop in and give some input. He does some beautiful work and I would like to hear how his cnc program on W8, W9's stack up against ones he has hand ported. Track tested results are always my favorite.

"I'd write a book, but would you pay to read it??????????????"

Absolutely, if there at least say 3? well known experienced proven porters contributing, anywhere from $100-250 a book. I also think different viewpoints are critical for the reader. Not sure if egos would allow a combined effort. That would be cheap info with the years of experience shared. Needs to be as textbook as possible, not a quick private library reading material read 3 pages at a time. However, I'm leery that the trial and error technique does not lend itself to printed page.

And here is the issue. You pay a 100% price for the CNC work and it's 95% (most time LESS than that). What Pittsburgh is seeing is exactly what I see.

Hell yes, if I could afford a CNC I would use it in a nanosecond. But I would FINISH the heads BEFORE they left me and not lie to the customer and tell him not to touch the ports.

I did read the interview with Larry Meaux (link is posted somewhere in the thread) and I have had 2 phone calls with him on surface finish. He said in the interview he has not done an A-B-A test on his finish. IIRC the interview is about 5 years old ands since then he has done SOME testing, but, IMHO, if he does not port at least 9 intakes to test, you really can't A-B-A them correctly.

I have tried to simulate (as close as possible) his finish and don't get the results he is seeing. Probably 5-6 reasons for that.

That's why you should find a head guy you can get along with, and do what he says.

CNC machines are nothing but computerized RE-production machines. As long as you understand a CNC finished head is still not finished, you'll be ok. You have a set of heads that have not reached their potential, but, by gar, they are CNC'd.

Books are nice, pictures are too but until you get you hands dirty and own a flowbench you are pissing in the wind. There are days when I grind and flow test a given head 10-15 times in one day. Tim Bowman Bowman Performance (a very accomplished head porter) and I were talking just last night about "short turn work and how your fingers play a BIG part in getting it right. I can honestly say I keep a pen and paper on my night stand as I often get up during the night and sketch something that came to me in my sleep. I will then apply it the next day to see if it works. I had to teach myself to try to visualize a port as a 3D object and port molding helped big time. Its great to be able to study something from every angle possible.

I'm no pro but I did learn from 2 of the best..
the first guy did all of the Mopar pro stock stuff
back in the 70s.. he did all the heads for the Woodward garage
guys which was the hot rod shop for Chrysler.. the other guy
that I learned from... he taught.. this guy and me hired the
same day at Chrysler and became good friends and I asked a
ton of questions just to see if things had changed... he was
the one who designed the swirl chamber.... I still like playing
with it but I'll never do it for a living

Here's what im not understanding from this conversation... why does a cnc have to be one size fits all? Why are cnc porters only using one specific port program on one particular head? I wrote over a dozen cnc programs just today. Are these guys lazy? I would have a whole list of different programs for each application if that was my bread and butter.

What's is the price difference between CNC and hand porting same head? As long as someone understands the difference with the end result before buying i don't see an issue. Now if you're worried if someone has reinvented the wheel, that has been around since day one, like I said before we all have to educate our customers so they understand what we have to offer. The CNC machine is nothing but a better tool thats quicker and offers repeatability which means lees money, not more, to charge the customer. Honestly I can't see how all eight ports could be the same with hand porting verses CNC( think of the surface area of the complete port,20-40 sq in). Now the final blending by hand is a no brainier, has to be done. Can you imagine making an engine, by hand, without using all the machines it takes

It doesn't, and in some cases you'll find people who will offer different programs for the same casting, or different castings w/ application-specific programs to offer some options.

But those guys are working w/ either highly specialized racing applications and raw castings intended for custom porting... or deal in a part of the performance industry where there are far more people to offer a variety of heads to (SBC & SBF).

Even my CNC'd Victors don't all flow the same (I've tested every intake port), simply because they're production castings w/ a certain level of core shift and have places where the CNC program doesn't touch each head exactly the same way.

The only way I'd expect a CNC'd head to flow exactly the same (give or take some small %) is if it starts w/ a raw undersized casting where the tooling touches basically every port & chamber identically. Any dropout means inconsistency, and applying a CNC program to any head already cast intended for use "as is" means that's a likely result.

Even then, I recall a porter who was doing a lot of CNC stuff w/ production based heads saying the final CNC'd version was a success if it flowed w/in some particular # of CFM of the hand-ported prototype which was digitized for the program. He didn't expect his own CNC'd heads to equal his hand-ported results, but it was a helluva lot faster to reproduce the basic port for mass consumption.

I am aware of this. But cnc porting in this thread is being addressed as a one size fits all non-custom option. And it doesnt have to be that way. 1. Custom hand port one port for specific application with flow characteristics you want 2.digitize 3. then put them in the heads with the machine. It doesnt mean you have to reuse that program for every head of that make and model

Get it "right?" So every head you have is ported to Prostock levels with welding, epoxy, sleeved pushrod and bolt holes and so forth?

I agree CNC is a production method, but let's not pretend that hand porting is all the same either. There's more than a few hacks and just plain average talents out there. CNC is selling for more than it's worth in many cases because clueless buyers are buying it. And that's fine, probably 75+% of Mopar guys don't need bleeding edge stuff because they're running bracket stuff.

My point was that the shop or porter could benefit from the machine doing much of the "dumb" metal removal. And frankly, there's a few porters who are under pricing their time for levels of performance that are simply beyond the reach of others. If people are paying 100% for 95% CNC and paying that same 100% for 100% from the hand porter, then that porter should be raising his prices. Because there is no substitute for winning, and if you need the "good stuff" to win, then that's all their is to it. Pay the man. S/F.....Ken M

CNC is the cats azz for duplication and reapeatibility.The program for the CNC is the magic.most programs are designed for maximum flow volume,minimum restrictions and optimum alignment.Each program is designed for the maximum effectivness for each particular application application.No one program is for "all" applications.

Continuing from the last post, this is my point. CNC, like much modern technology, is for freeing up men from the drudge of mindless repetitive labor. They're like illegals, without the drunk uninsured driving and knife fights in bars.

People run their gums about CNC stuff in their car because for most people it's not about the racing, it's about the jaw jacking.

Like I said, if a hand porter is doing 100% work for 100% cost, and the CNC guy is doing 90-95% work for 100% cost then the hand porter should be charging more, and he's a dope if he's not and making the fact that his stuff is better well known.

IMO, the "proper" place for CNC in racing (as opposed to bracket) is for doing billet heads and cutting full ports and chambers in unfinished castings (edelbrock pro-ports and the like). In addition to doing all the prep porting for the hand finishing.

And then there's stuff like TFS is doing with heads being designed for and finished on CNC, giving better performance at lower cost than doing the full Monte with aftermarket porting. S/F.....Ken M

Sorry but I'm not getting this post. Duplication yes, but in EVERY case or head I've tested it has been BAD duplication. Flowbench shows it and the track times do too.

John, what do you mean by bad duplication? The machine wont fix a bad design, it has to be good before its copied. If its wrong, its the cylinder head specialist fault for cutting out a junk port. Nothing to do with the machine, its just copying the hack's work.

I'm telling you that EVERY CNC'd head that I have ever tested has been pathetic and needed major work. Upper lifts on every head went turbulent and started backing up in flow numbers. Testing proves short-turn not capable of maintaining control and the air goes straight across the bowl shutting off air flow going across the top of the port. You can hear it happening. (think garbage disposal)

John, what do you mean by bad duplication?



I'm telling you that EVERY CNC'd head that I have ever tested has been pathetic and needed major work. Upper lifts on every head went turbulent and started backing up in flow numbers. Testing proves short-turn not capable of maintaining control and the air goes straight across the bowl shutting off air flow going across the top of the port. You can hear it happening. (think garbage disposal)

I understand what you're saying but I agree with smell, it's only a machine and only as good as the person programming it. Sounds like the CNC guys don't know what they're putting out, just machining a pretty product to sell, and making quick easy money. This happens in a lot of products. Someone does all the R&D then another guy somewhat closely copies the product with no money invested, pure profit, customer screwed because they listen to the hype.
Might add, if you had the CNC machine I'm sure you would not machine those bad areas that you're talking about. Do you think it's possible to duplicate you port work to the fine line, what I'm saying is the machine capable?

BINGO!!!!!!!!!!!!!! And I'm not saying there aren't GOOD cnc'd heads out there. I just haven't found them yet.

John all I can say is thank you again for this post. There will be some here who will bash you now for being so forthright. I have seen this in the past as well. When it happens just ignore them. Your points are valid. The performance of your cars speaks to your ability. I just wish there were more of these types of discussion on this forum. It is a learning experience for me and others I'm sure.

And to the other contributors on this thread. Thanks for your input. Jim

CNC porting has become a sales gimmick of sorts, and 99% of the heads on the market are fairly generic. As has been stated in this thread already, if the port being copied isn't great, the machine isn't going to make the head any better. That said, a cnc ported head will be more consistent from port to port than a hand ported head.

I can think of two CNC programs out there I know are good
W5 CNC program at Modern
Small block Eddie CNC at Modern
I would wager there are plenty more, but can verify as fact only these two, based on track results, which to me is all that matters.

That info Don has posted is the kind of info I would like to see others offer. Thanks Don for sharing.

Here's a letter I received from a good Friend, Tim Bowman of Bowman performance. He doesn't post very often as he is usually busy teaching or in the shop building well thought out, high horsepower race engines. He was taught by one of the best so read this on his thoughts.



Been HAND porting heads 40+ years
Got to spend some time with probably one of the best hand porters out there, Joe Mondelo, RIP Joe I miss your input.
Proper hand porting has become a lost art.
Been flow testing for over 30 yrs of those 40 yrs
Its and ugly unrewarding job until you put them on and engine and make power.
I have never flow tested a cnc head Brand x or Mopar that ever flowed the claimed numbers AND didn't have major issues in the flow curve.
I'm with you on this one John, upper lift flow on a big head that should do it. Joke!
Garbage disposal? Sounds like someone took big crap in front of a big fan. That's what you got,crap
I promote cnc head sells, only with the plan than additional work needs to be done, and i charge on top of that.
cnc gets the rough work out of the way, John knows the time it takes to port n flow heads.
Repeatably JOKE! 40 cfm spread on the same head? That includes Hemi heads
Valve jobs as delivered, Lets not even go there. This is a big part of the final product
Also, on a cnc head, there are times where you can,t fix a problem they created without re- weld or sometimes epoxy
Cnc has a place in the market for those that do not have the skills to port heads, absolutely not offense intended to them.
But the product is not where it should be in this day and age.
Some of the cnc porting final finish looks like they cut lose a rabid beaver in there, come on Really?
Got so many cnc duplicate heads in here that are not even close to each other, wtf? is your equipment that wore out? Got any QC going on here ?
if your going to port heads for power/in all different applications better have a flow bench. Any novice can improve a cylinder head with in reason.
If you work with a flow bench, you need time to interpret what it is telling you also , it takes time and experience, I know John knows!
Lastly, there are a boat load of top self cnc heads being supplied out there, doing what there supposed to do, you just got to know who they are
and they are spoken of on Moparts.
My input John, feel free to post this, As for hand head porters, keep on grinding. Tim Bowman, Bowman Performance

^ good stuff. Now all this thread needs to balance itself out is a good head porter who actually has a centroid and does more than copies cast ports and puts little shiny cutter marks in everything.

I think what some of the problem with CNC heads are most of the mass produced stuff is its more of a shine job than a real performance head.

No way would I hand port w9s or w8s but my CNC stuff all gets some hand finish work

Just valve job and blend can kill a good CNC port if done wrong.

I have updated some HAND PORT w9s and port to port before we recut them did not look bad but after you can see how far off hand port stuff can be.

Here is some pictures of bad a$$ CNC WORK. (Note valve job blend not done)
This is TRD cup head cut in house by Toyota.

Just like hand porting most of the time you get what you pay for.

$1000 CNC job most of the time will need some work to make good.

If you start out with bare Indy 360-whatever and hand port to max potential it would take 40 plus hours at $50.00 per hr. = $2000.00


The other deal with CNC castings have thin spots all the time to make money you can't junk lots of heads so most mass produced heads are backed off little vs what hand port master was.

My w9 program is on the "edge" gets little thin but it's not mass produced

I also have 3 intake programs for that same head to fit wide range of builds.
So you can cut smaller port and hand finish for application or cut the big one and add the weld that's needed with the customer knowing up front heads will have holes into water when done and need weld.

Some of my CNC cut heads with quality valve job.

I really like the one line your friend said... which is
VERY TRUE... porting gets the bulk of the work out of the
way... then its the fine tuning... most people not realize
that it takes just a minor bit to change things... thats
when you either know things or not.. a bit too much and you
can screw it up also... believe me I know when I started

I like the directional lines in the Toyota head...

How valuable is hand finishing after CNC?
That depends on how small the tool pass increments are. A program that makes 10,000 passes 1 micron apart won't need any "fix up" work.

Tool deflection can't be eliminated, but how many axes of rotation the head can make, and how small it is will reduce it (along with making very small, slow passes).

"Designing a port in CAD" doesn't mean what it sounds like. Just like fuel injection, CAD knows only what you tell it - it doesn't answer questions or compare possible solutions. You're thinking of CFD.

Does anyone out there still think CFM is the goal?

You sure know how to get your point across. Was there a point?

And your point is that you have no manners?

Those Toyota ports look great. I've seen a lot of super nice CNC work over the years. MCH always had nice stuff, Chapman had great stuff, etc.

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. Someone with a hand grinder is as likely to mess it up as they are to improve it.

and to me that is the difference between a CNC port job from a dedicated porting shop as opposed to the aftermarket head CNC work, the dedicated shop is more likely to insure that the job is as good as they can do as opposed to XYZ head company that mass produces them by the hundreds and sell the claim that their heads are CNC ported, yep they sure are looks like someone ported them with ball nosed end mill at 500% feed rate.

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.

Chapman is the last set of heads I bought... very nice CNC
stuff and I still touched them up.. only due to the spacing
of the cuts... I didnt get carried away but did pick up 3 cfm...
that was on the same machine

NASCAR has all been CNC'd since 1991 when they mandated that each manufacturer had to use one head for all teams. S/F.....Ken M

Alot of varied opinions here, good points 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 in 79-80 when this started vs cnc 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.

The same thing happened more or less, so the tractor ended up going to europe and being sold in the mid 80-s.

But they never did find the nitrous bottle that was hidden by the water tank, built around it. It was hell on crankshafts and blocks.

The project head I mentioned was a single cam and only twin t-17s in series which was the norm then.

I'm sure there are but if I personally was going to set up and sell a CNC'd head I would want to see dyno and track results BEFORE I purchased and set up their program. As I said I've never flow tested a CNC'd head yet that did not go turbulent. Not saying they aren't out there. Those Toyota heads are state of art and are not your typical store bought program. Trouble is now is that the big companies don't really care if its right or not.

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?

Or because the inlet radius used could be causing it...if a port is turbulent, sometimes flowing with the intake on will help and I've seen this run pretty good in a car.
My old W2 headed 360 was like that. It ran well for what it was.

I have 1/2 thick radiused lexan inlet plates that I use for every head that I flow so that isn't an issue. Almost every head is tested with an intake mounted as my Friends that I do work for are usually there to see the before and after numbers of not only the head but also with the intake bolted on. Each and every head and sometimes every port are checked for air-speed throughout the port which will show you exactly where the issue is and what needs done to correct the problem. They could and should be checking this too but its all about the "bottom line" for them and many others.