Hand porting vs Cnc porting

Posted By: dannysbee

Hand porting vs Cnc porting - 11/06/13 05:54 PM

Why would a person prefer a Cnc head over a hand ported head done by a talented porter? The cnc head is only as good as the original head that was digitized to program the Cnc mill. Just because someone has a Cnc don't mean they are a head porter. Just courious what the fascination is.

Posted By: Thumperdart

Re: Hand porting vs Cnc porting - 11/06/13 06:01 PM

Lots of time is spent hand porting to obtain the maximum/best port as I understand it then it`s probed and measured and transferd to a reproducing cnc program so each port is perfectly duplicated..............in laymanns terms..............

Some guys still do it by hand though.

Posted By: dannysbee

Re: Hand porting vs Cnc porting - 11/06/13 06:28 PM

I see it as labor saving device and yes the ability to duplicate precision work done by the porter. It still requires skill, precision and testing by a person. I just know I see people handing out good money for heads that are cnced and have no idea who did the work for the programming. Just because heads are cnc ported don't mean they are the best thing since pockets on a shirt.

Posted By: d7cook

Re: Hand porting vs Cnc porting - 11/06/13 06:33 PM

Quote:

Why would a person prefer a Cnc head over a hand ported head done by a talented porter? The cnc head is only as good as the original head that was digitized to program the Cnc mill. Just because someone has a Cnc don't mean they are a head porter. Just courious what the fascination is.

Thats why you go to CNC porter that knows how to hand port. They develop a port by hand then use a CMM to digitize it. Also for $950 to $1100 you get the intake ports, exhaust ports and chamber done plus a valve job and decked to whatever CC you want. It's all or nothing but your heads are completely done.

I also believe that there's power and consistency to be gained by having every cylinder flow the exact same amount. Maybe it's just me but the engines I've built using CNC heads run a lot smoother through the rpm range.

Posted By: pittsburghracer

Re: Hand porting vs Cnc porting - 11/06/13 06:34 PM

A cnc'd head is only as good as the head it was copied from. Bad original job by porter lots of bad copies from cnc.

Posted By: Crizila

Re: Hand porting vs Cnc porting - 11/06/13 06:41 PM

Quote:

Just because heads are cnc ported don't mean they are the best thing since pockets on a shirt.

Very true. CNC porting is a labor saving device, and in that context, they are hard to beat. Repeatability is also good. That being said, IMO, a professionally ported head is still hard to beat. Also IMO, a combo of the two is the way to go. Get them CNC'd and then finished by a professional porter.

Posted By: dannysbee

Re: Hand porting vs Cnc porting - 11/06/13 07:02 PM

I agree that the process is awesome and should be able to save the consumer some money on the end product. That is great. But too many times I will be talking to someone about their combination and they will get to the heads and say that they are Cnc ported but when asked by who the answer is don't know, bought them off the internet. Then go on without a second thought. Seems to me a lot of people think just because their heads were cnced it was a professional job. I think not necessarily so.

Posted By: SSDart

Re: Hand porting vs Cnc porting - 11/06/13 07:29 PM

CNC porting makes for the best process.... Given the original ports copied from are good. Like anything else junk in junk out. That said, a hand ported head can be good and can be bad.......

The best case........ Would be a real good porter concentrating on making good ports to copy, then CNC re produce from there.
As we all know porting heads is very hard work and getting a complete head quality ported is a ton of work and money...... making any quality work expensive..........

Posted By: BradH

Re: Hand porting vs Cnc porting - 11/06/13 08:24 PM

Comments:
1. Unless the CNC program is run on a dedicated "Pro Port" core, there are still liable to be drop-outs and other casting-related differences between runners on a CNC-ported head. So, in that case the expectation that each port flows identically simply isn't true.

2. CNC programs run on typical production heads (not the raw "Pro Port" cores mentioned above in #1) often require someone to hand-finish areas such as the bowl blend and valve seat transitions into either the bowl or chamber.

3. I've seen "by hand" ported production heads that are as about as close from runner to runner as those production heads that still need to be hand-finished like I mentioned in #2.

4. I like that one of the porters who does a lot of CNC work these days mentions it's his goal that his CNC heads flow w/in 5 CFM of his hand-ported prototypes once they're ready to ship. Right, his CNC'd heads don't flow as well as what they're based on done by hand.

Posted By: B G Racing

Re: Hand porting vs Cnc porting - 11/06/13 08:52 PM

The benifit of CNC is for production work(repeatibility).Most CNC programs are developed from a hand ported set of heads that produce desired numbers.If you only do a few sets of heads then hand porting is fine but if your doing a volume of sets of heads and have a desired standard of numbers then CNC is a must.What normally would take 40 hours of hand work to achieve will be done in only a few hours.Most head porters can only charge X amont of dollars for a weeks work.IE:$900 to full port a set of heads in 40 hours and do 4 sets a month= $3600.With a CNC program 2 sets can be done in a day at $900 per. $1800 per day X 20 working days in a month=$36,000.Admittedly the inital cost is highly expensive for a multiple axis CNC machine,but if head work is your business it can payoff rather quickly.

Posted By: d7cook

Re: Hand porting vs Cnc porting - 11/06/13 09:27 PM

Quote:

Comments:
1. Unless the CNC program is run on a dedicated "Pro Port" core, there are still liable to be drop-outs and other casting-related differences between runners on a CNC-ported head. So, in that case the expectation that each port flows identically simply isn't true.

I had a set of Performer heads CNC ported to MW but kept the valves the same size and experienced some of this. The Victors I had done started as std port and went to MW with a 2.25" intake and I did not experience any drop outs or casting related problems. When the Victors were done I was directed to supply std port castings which I assume is because of this issue.

Posted By: MRMOPAR622

Re: Hand porting vs Cnc porting - 11/06/13 10:44 PM

Quote:

Quote:

Just because heads are cnc ported don't mean they are the best thing since pockets on a shirt.

Very true. CNC porting is a labor saving device, and in that context, they are hard to beat. Repeatability is also good. That being said, IMO, a professionally ported head is still hard to beat. Also IMO, a combo of the two is the way to go. Get them CNC'd and then finished by a professional porter.

You are correct it takes a professional head porter a lot less time to finish up a set of CNC heads.But you need to make sure you have the right person to CNC the heads at the start.I have found it best to take them to the professional head porter and let them have the cnc work done or tell you who to take them to.