CNC vs Hand Ported Heads..

[fullahotair]

Just curious as to what the consensus is with respect the two. Naturally hand ported has more of an human error element and results may/will vary from head to head and a CNC head is very repeatable....

but on average do you get better results from a CNC head or a professionaly hand ported head? In other words, will a 1200 CNC head be comparable to a $1200 hand ported job...

I suppose at the end of the day the flow numbers tell the story...

Thanks,
Nate

 

[ESP Products]

I would side with CNC. Yes human error is a big factor. Did the guy have a good day or bad? Was it ported on Monday morning or Friday at 4:30 pm? You get the idea. CNC works for companies like us, because we now have a reliable, consistant product. When we put together a package we know what to expect. The CNC process overlooks variation in the head and takes out what should be taken out. It will not exadurate low spots and so on. Also, because you pay mostly for the labor, the CNC is usually the better deal. A $1600 head can be CNC'd for $1300, because of the time savings (not real numbers). So if you have 2 heads that are both $1200, the CNC would likely be a better head.

Hope this helps you.

 

[fullahotair]

Thanks for the reply...can a Cnc machine touch every part of the head that a hand port job would? Or do you have to do some hand work after the cnc process? Thanks...nate

 

[ESP Products]

Thanks for the reply...can a Cnc machine touch every part of the head that a hand port job would? Or do you have to do some hand work after the cnc process? Thanks...nate

Yes and Yes. The CNC can do the full job and can touch every place in the head. The final assembly is done by a human, so some blending is performed. It's usually minor work that goes along with installing the valves.

Hope this helps you.

 

[Nick Micale]

.............. I suppose at the end of the day the flow numbers tell the story...

Thanks, Nate

Actually, that is not a true statement.

What tells the story is how much HP and torque you get at the end of a dyno or track run. Many racers and head shops have seen better performance from comparable heads that have lower flow numbers.

There are other factors in head porting that determine performance like port velocity, ratio of intake to exhaust flow and other data points.

Heads for blown application and NA also have differing head flow criteria for best performance.

A CNC head will give more consistent numbers for a given application, but LOTS of trial and error bench and track testing from hand ported heads must be done to determine the optimum design for a given power/flow level.

One of the best examples of this are the heads on Ted A's GN that were initially done by TA Performance, and then "massaged" by DLS before installation.

I know of TA heads with higher flow numbers, but none performed like Ted's car. :biggrin:

Your original question is too general for a specific answer. Since you did not specify your combination or performance goals, an of-the-shelf CNC head may give you too much flow, or not enough for your situation.


On the flip side, if your build and use application is close to matching a specific CNC head, then this can be a good choice, and possibly cost less than hand porting.

 

[fullahotair]

Nick, thanks for the reply...

Also thanks for going into some of the details associated with a "good" port job. I always thought the more flow the better, but as you mentioned, that it isn't really an accurate statement for the reasons you provided. I appreciate the information and insight.

As for my details, I am still at a very high level with respect defining my engine combo, but i am anticipated doing a bottom end that would be capable of withstanding 10's, and then run mid to low 11's with ease....and safely... Right now, I am just doing my homework and trying to educate myself on various items. Once I feel comfortable with what I came up with, I'll post it up to get some feedback...

You mentioned spec'ing the heads to match with the rest of the build. Would it be the cam that is most sensitive to the heads?


Thanks for your time,
Nate

 

[JayC]

You should also keep in mind that core shift keeps CNC porting conservative. They are mostly cut out via CNC and finished by hand. Champion's CNC heads dont flow quite as well as their older heads but they are very close, within a couple of numbers.

Just depends on how much money you want to spend. I have a set of iron heads on Shane's TFS car that flowed well over anything you can get CNC ported but there is a small fortune invested in them.

 

[ESP Products]

You mentioned spec'ing the heads to match with the rest of the build. Would it be the cam that is most sensitive to the heads?

Big runner heads, aluminum, can help HP, but hurt torque. Iron heads are suggested for most street (and race) applications for this reason. As you mentioned in the above quote, the cam and head combination is closely related, that's obvious. If you know what the head flows, and you know this number every time (benefit of CNC), you can suggest cam grinds more accurately. You can choose a cam that will assist the head in obtaining the optimum flow ratios. The same goes for the rocker ratios. As Nick said earlier, velocity is important not just flow. The choice of heads is more based on your budget. Any head can outperform and other head if enough money is spent. Just like any car can be made faster, with alittle more time spent. If you're looking for easy 11s, then almost any head will do that for you.

Hope this helps you.

 

[S2V6RACER]

Actually, that is not a true statement.

What tells the story is how much HP and torque you get at the end of a dyno or track run. Many racers and head shops have seen better performance from comparable heads that have lower flow numbers.

There are other factors in head porting that determine performance like port velocity, ratio of intake to exhaust flow and other data points.

Heads for blown application and NA also have differing head flow criteria for best performance.

A CNC head will give more consistent numbers for a given application, but LOTS of trial and error bench and track testing from hand ported heads must be done to determine the optimum design for a given power/flow level.

One of the best examples of this are the heads on Ted A's GN that were initially done by TA Performance, and then "massaged" by DLS before installation.

I know of TA heads with higher flow numbers, but none performed like Ted's car. :biggrin:

Your original question is too general for a specific answer. Since you did not specify your combination or performance goals, an of-the-shelf CNC head may give you too much flow, or not enough for your situation.


On the flip side, if your build and use application is close to matching a specific CNC head, then this can be a good choice, and possibly cost less than hand porting.

I've also heard of WAY higher flow numbers also. I'm not sure if their heads were CNC'ed by TA and "worked" to get the big numbers they claimed or if they started with a fresh set of heads.

I am very happy with my TA CNC port work and Dan's magic.

 

[JayC]

The TA heads we have for Shane's TSM car flowed 313 at 600 I think.. I could be off by a few numbers, Id have to go back and find the original post. My head guy said he could have gotten them over 330 very easily but that would have sacrificed a lot of low lift numbers.

 

[fullahotair]

Thanks to everyone for responding. I got a lot of valuable information out of the input you guys have provided. I have seen before where it was mentioned to stick with ported irons for street, but never found out exactly the basis for that, but not i know.



Thanks!
Nate

 

[Dreamcar86]

Interesting thread. It has always been my understanding that head porting is more critical on a N/A car. At what point does it become more critical on a forced induction car? Are we talking about cars running 10's and quicker?

 

[ESP Products]

Interesting thread. It has always been my understanding that head porting is more critical on a N/A car. At what point does it become more critical on a forced induction car? Are we talking about cars running 10's and quicker?

Head porting is a basic, on any engine. Our Buicks can run into the 11s without any engine work. I would say, conserv'ly, 11.6s with just bolt-ons. The only difference with a N/A engine and a turbo engine is that the turbo must be large enough to keep up with the heads, or you run into efficiency issues with the turbo. Almost any after-market turbo would fit the bill and be able to support a good set of heads. I have seen a good set of heads/cam/intake add as much as 150 hp to a set-up (105 hp w/ just heads & intake). I would say 150 hp is a critical number.

Hope this helps you.

 

[JayC]

150 horsepower from JUST heads and cam?

Were they sprinkled with pixie dust and unicorn poop too? Thats about 3x what most people will tell you they're good for.. you must have a hell of a head porter.

I guess if you wanted to have some GREAT dyno numbers you could build a 9 second combo, dyno it with stock heads and cam and put a set of Champion Rs and a solid roller in it and see huge gains but dont sit here and try to tell "Joe Everybody" they're going to see 150 horsepower from heads and cam.

 

[ESP Products]

I spoke with Tom at Champion and I know his numbers are up there. We've been providing this package for years. Again, a good Head/Cam/Intake package can yield 150 hp. I've had customers come in requesting 100 hp. CNC heads and a balanced intake (stk) were installed. Why? Because they had the right combination of existing parts to justify this upgrade. The customer gained 105 peak hp. He gained even more on the upper end. We have been CNC'ing heads for many years with these results.
Sorry guy, no 9 second engine build and no solid roller. As a matter of fact, the example I stated was a flat tappet cam and a street car with a "Trans Plus" for tuning. You'd get more with a good roller cam. Now I didn't say anyone could do this. I said the right combination of parts; I said a good set of heads/cam/intake. Not everyone has that, so I understand. This is also not a trailer queen, this is a street car.
Hope this helps you.

 

[GNBRETT]

lol

 

[Ed Valvo]

So far I've increased 7 mph in the 1/4 mile from heads, intake, and 206/210 roller cam. This is with less boost too. I'd imagine running the same boost that I did with stock heads would net greater results.