CNC ported versus hand ported heads

[bugnut68]

Researching head options for an engine project I'm developing... just wondering what the general thoughts are on CNC versus hand ported heads?  I only ask because of the similarity in prices between a set of CNC heads and hand-ported heads that I have researched.  Just wondering what the benefits and advantages are to each type of product.  I'm by no means a guy looking to extract every last possible pony, but am looking forward to having some fun with my first stroker build.  Thanks in advance for any general comments!

[bugnut68]

Anyone?   

[neil68]

I had my CB Ultra Mag Plus CNC 044 heads ported by K-roc and got 38 more WHP.

The compression ratio was increased by 0.9;  42 mm intakes were replaced with 44 mm valves and the jugs were increased from 90.5 to 94.  Based on this info, I believe the porting was an important factor, as previous changes such as 90.5 to 94 have not shown such a dramatic increase...

[58vw]

ahhh...there is a debate...

[ugly duckling]

you make the choise you can have this.  . grantit not all of them look this way but come on people have just a bit of pride will ya. UD.

[ugly duckling]

or you can have this and the love and pride that goes with the product in every custom set. you make the choies . UD  .

[roland]

Do you think that the "grooves" of the CNC porting affect the flow?

[ugly duckling]

real hands and real brains will always lead the way. the SR71 black bird wasent built by a computer. THE END . UD . 

[John Rayburn]

You'll always have my business, Jeff.

[bugnut68]

I took a look in the garage last night at what I've got to work with, and initially I thought I had either a pair of 040 castings or 311 castings to work with (fresh, non-ported but bored to 90.5mm heads).  Turns out I have one of each, lol.  Not sure where I'm going from this point on, but I'd rather have uniform heads, unless it makes a difference?  The specs otherwise are the same, but I just noticed I had two different castings upon closer glance last night.

What are the pros and cons to each of these castings, as I'm not real famiiar with these kinds of details?

[Udo]

I took a look in the garage last night at what I've got to work with, and initially I thought I had either a pair of 040 castings or 311 castings to work with (fresh, non-ported but bored to 90.5mm heads).  Turns out I have one of each, lol.  Not sure where I'm going from this point on, but I'd rather have uniform heads, unless it makes a difference?  The specs otherwise are the same, but I just noticed I had two different castings upon closer glance last night.

What are the pros and cons to each of these castings, as I'm not real famiiar with these kinds of details?

The 311 heads have a better casting , you can be lucky to have a set .

The cnc porting is a good and cheap way to get good ported heads . But if you do some hand work on them you get more flow that is for shure .
So i would say hand porting is more expensive . i take 040's , relocate the spark plugs in 2 angles and move from seats . weld the chamber and do the porting . That is a lot of work .
If you want cheaper i take bare cnc heads and do some work on them

Udo

[bugnut68]

Would there likely be any adverse effects to having two different castings, despite identical valve sizes, etc., on an engine?  Since I apparently have one 040 casting and one 311 casting, I'm considering selling these heads and starting all over with something else.

[Bruce]

Ryan, don't even think about putting one dime into those mismatched heads. Even if you could find a mate for either, you would be better off starting with some NEW Mexican 043 heads.  Many well known head porters agree this is the best stock casting in existance.  The alloy is very strong.  It also has one of the best exh ports you can get. And they are so incredibly CHEAP!  You can get them in 40x35, and have them ported.

[Neil Davies]

Surely it would be the ideal situation to have a CNC machine "rough out" the head to an experienced porters specs, and then the porter finishes them by hand? I remember Richie saying that the nice thing about a CNC head is that when you torch one, you can replace it with an identical head. Of course, a machine can't replace the years of experience and knowledge that makes someone like Jeff so valuable to the industry.

[bugnut68]

Thanks, folks, I appreciate the insight.  Bruce, that was my instinct, but wanted to confirm as I don't have a working knowledge of the various castings.  I always prefer keeping things matched up whenever possible.

[Torben Alstrup]

I agree. A hand ported head will in 99% of the time be able to do a better job than a CNC in this case. Among other things because the CNC will have a hard time making the perfect surface.
But the above "comparison" is not worth much. The displacement is increased. Then the first 10 - 15 hp is easily found by just the enlargement of the valve, + some % with more displacement. The CR altered by 0,9, is good for about 4%  ? THEN you can begin to talk about the difference between CNC and hand porting. Next is, do the engine need more flow(?) too much flow is as bad as not enough
T

[JS]

Torben, I completely agree with you. I think one of the differences Jeff is showing is how the valve seat sits and blends on the CNC compared to the hand ported one.

[RFbuilt]

i always thought, cnc ported heads are there, to save time and cost on heads getting the overall "shape" of the port and still need to be hand blended and cleaned up , then a good serdi valvejob   

but then apparently some (based on reading around) actually run heads that are cnc ported and not hand finished yet? 

1- cnc porting (port and chamber) to get the shape needed and save time vs hand done
2- hand finished to how it needs to be (like it was hand ported all the way or cnc for starters)
3- cnc is as good as the head they used for digital mapping.. (if the head they mapped sucks or works for 1.. may not work for all)
4- cnc unfinished heads would prolly have a hard time competiting with a specially crafted hand ported head
    granted that even a 5 axis cnc  myt not reach certain spots in the head , that a hand can reach

thats my take..  ofcourse  that take has way less experience towards vw hehe  but on a different platform this is what i understood it to be (honda  LOL) 

hopefully UD or Udo could clarify things on my post.. if i worded or misunderstood the concept of CNC porting..

[Udo]

I think you are right . CNC ported heads are good for all who do not want to spent that much money . I think this is why CB started this kind of heads .
BUT i make some more differences between street use and racing engines . This is why i most use original heads and do all the work . Every engine and head builder has his own experience

Udo

[RFbuilt]

yes thank you Udo for ur comment..

i wasnt saying one is wrong or one is right..

was pointing out.. like you yourself do your own work..

if you could cnc map 2 kinds.. 1 port lay out for street (based on your developments and sumthing u think would cover 1.8-2liter)
                                          another port lay out for heavy street and competition prolly for 2-2.3Liter 
 it could save "time" maybe its not about saving cost for the buyer.. but the waiting time could cut it shorter
but for sure.. "as is" cnc ported heads would be less beneficial.. so im sure you still would hand finish the ports per application including valvejob etc..  and chamber cleaning..

not to say it could eliminate most of the hand work? but ofcourse every 2-3 heads out of the 10 lots you port.. prolly is for a full competition use.. that the buyer wants the best.. not the fastest turn around.. so mos def hand work is still needed.. 

^^^^^ i always looked at it this way.. but again.. lack of experience in the VW world.. and based on reading
           there are alot that run fresh cnc'd heads non hand fnished as is? 

based on honda platforms.. we do use cnc ported heads but its always in "bare" status  and needs clean up and finishing according to the engine lay out to be used... but in some cases , if the engine is a little off the normal side of things.. it is custom ported by hand.. from start to finish..

very interesting thread and discussion though ME LIKEY!  hehe

thanks Udo for the insight..

[ugly duckling]

if i had 150.000$ to blow on a machine yes i would probibly buy one. but would go more into depth on keeping some of the structure points of the cly head intaked. not just going in like a lawn mower and shaving away important areas that should have been left alone for structure and flow purps. then would hand blend like i always do for that extra touch that a cnc machine will never be able to duplicate. yes they have there place in the industry but are far from perfect. . and as far as these fancy serti valve jobs that are suposed to be the CATS MEOW well every one that i have ever seen when the heads are new come into my shop i could see total day light thure them. i gusse its the guy behind the wheel just wanting to get a pay check. he dosent care he dosent lap the valve after. he just lifts to fast on the cutters and like a fly cutter you know what happens you have a step. this is why i still like stones 360deg of contact at all times . more of my two bits. UD .   

[RFbuilt]

very interesting UD!! much apriciated.. i do agree.. cnc and even serdi etc.. its as good as the operators skill and knowledge..

hope u didnt think i was furthering the debate between cnc and hand ported units..

i was more stating (or wondering haha)  that cnc has its place , much like u said.. and i was thinking
it could be of benefit as the starting point (work starts) on fresh head's then finished up with the magical hands of a porter.. 

^^^^ ofcourse cnc is as good as the head that was used for mapping..  so in a sense.. if UD maps a UD ported head thru cnc.. im sure its gona be a very yummy starting point!  ehehe