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Re: Hand or CNC Head Porting ???
[Re: dizuster]
#504020
10/22/09 06:47 PM
10/22/09 06:47 PM
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Anonymous
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Anonymous
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CNC porting is a program designed for a specific head, the cnc program will get you the maximum allowed porting to achieve maximum flow numbers.
a hand porter can not get each chamber exact giving you different results from head to head.
also theres a chance that a hand port job possibly could hit a exhaust port water jacket. ask me how i know. no more hand porters for me, its CNC or nothing.
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Re: Hand or CNC Head Porting ???
#504021
10/22/09 06:49 PM
10/22/09 06:49 PM
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Joined: Jan 2003
Posts: 32,394
Quicktree
I Win
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I Win
Joined: Jan 2003
Posts: 32,394
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Quote:
CNC porting is a program designed for a specific head, the cnc program will get you the maximum allowed porting to achieve maximum flow numbers.
a hand porter can not get each chamber exact giving you different results from head to head.
also theres a chance that a hand port job possibly could hit a exhaust port water jacket. ask me how i know. no more hand porters for me, its CNC or nothing.
isn't the CNC program obtained off of a hand ported port? they have to get them from somewhere 
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Re: Hand or CNC Head Porting ???
[Re: Quicktree]
#504023
10/22/09 06:57 PM
10/22/09 06:57 PM
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Joined: Apr 2005
Posts: 12,271
Overpriced Housing Central
RobX4406
I Live Here
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I Live Here
Joined: Apr 2005
Posts: 12,271
Overpriced Housing Central
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Is the cnc the right port for your application?  If porting is a one size fits all deal then cnc might be the best, but, that's not real world. cnc's are based/probed/digitized off hand ported from what I've seen.
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Re: Hand or CNC Head Porting ???
[Re: Quicktree]
#504024
10/22/09 06:58 PM
10/22/09 06:58 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Quote:
Quote:
CNC porting is a program designed for a specific head, the cnc program will get you the maximum allowed porting to achieve maximum flow numbers.
a hand porter can not get each chamber exact giving you different results from head to head.
also theres a chance that a hand port job possibly could hit a exhaust port water jacket. ask me how i know. no more hand porters for me, its CNC or nothing.
isn't the CNC program obtained off of a hand ported port? they have to get them from somewhere
that is correct, lets just hope the head porter wasn't hitting the sauce or pipe when he was designing the program. 
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Re: Hand or CNC Head Porting ???
[Re: sg66mopar]
#504026
10/22/09 07:17 PM
10/22/09 07:17 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
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master
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Posts: 7,506
Az
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CNC head porting is over rated - the shops that bought these machines have to pay for them some how and they do cut way down on shop labor costs, as hand porting is very labor intensive. I am by no means a pro when it come to head porting, but a few years back I ported a set of 915 casting small block heads. I was fortunate enough to have a brother that ran the flow room for Navistar at the time so I had unlimited access to a flow bench. We flowed the intakes in their stock configuration and found a max flow variation of 3.6%. I was able to improve this to 1.6% by doing some methodical hand porting. I'm sure that someone who does this for a living could blow those numbers away. IMO, a professional hand ported head will outflow a CNC machine ported head every time.
Fastest 300
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Re: Hand or CNC Head Porting ???
[Re: Bob_Coomer]
#504028
10/22/09 07:36 PM
10/22/09 07:36 PM
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Joined: Jan 2005
Posts: 3,635
Oakland, MI
dizuster
master
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master
Joined: Jan 2005
Posts: 3,635
Oakland, MI
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Quote:
Quote:
CNC is repeatable, but can't take advantage of making the port as big as possible because of casting shift.
Why would you want the ports larger on core shifted heads?
That's the point. CNC programs have to work on every single head, even the one's that are core shifted. That means the programs have to be conservative (small) to account for core shift. A hand porter can take advantage of a good casting...
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A good hand porter can feel/hear when the walls are getting thin.
Really?
Now thats a skill I would love to know..Im sure its possible at the point were its almost through the side of the runner...LOL..
But at this point the heads are trashed anyways.
I kid you not, a good head porter can hear when the port wall is getting too thin. You can hear the grinder bit change pitch. I suppose grinding on heads 10 hours a day for 20 years will do that to a guy.
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Re: Hand or CNC Head Porting ???
[Re: Crizila]
#504029
10/22/09 07:41 PM
10/22/09 07:41 PM
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Joined: Jun 2005
Posts: 793
Utah
topbrent
super stock
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super stock
Joined: Jun 2005
Posts: 793
Utah
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Pick a reputable shop, either way. There are many good shops to choose from, but these guys are the perennial favorites here in Moparts-land. Hand Porting: Brian @ IMM ou812/IMM Dwayne Porter @ Porter Racing Heads fast68plymouthRyan @ ShadyDell RyanJ CNC: Jeff @ Modern Cylinder Head. Modern Cylinder Stay away from the backyard know it all types. A big mouth and a set of carbides can do a lot of damage! Do you really want to be a guinea pig for some hack? Go with the guys who have ported many sets of that that head type and have good routines and a proven history of great performance.
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Re: Hand or CNC Head Porting ???
#504030
10/22/09 07:42 PM
10/22/09 07:42 PM
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Joined: Jan 2005
Posts: 3,635
Oakland, MI
dizuster
master
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master
Joined: Jan 2005
Posts: 3,635
Oakland, MI
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Quote:
CNC porting is a program designed for a specific head, the cnc program will get you the maximum allowed porting to achieve maximum flow numbers.
Not true. Why do you think Indy offers several different CNC versions of their heads? It's because not all CNC port profiles are created equal.
Quote:
a hand porter can not get each chamber exact giving you different results from head to head.
also theres a chance that a hand port job possibly could hit a exhaust port water jacket. ask me how i know. no more hand porters for me, its CNC or nothing.
A good hand porter is not going to break into the water jacket. There are 1000's of heads ported around the country by hand that don't break into the water jacket.
CNC is used because it's fast, easy, and repeatable. That means that CNC ports are set up to please the masses. A good hand porter can tailor the port to the motor...
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Re: Hand or CNC Head Porting ???
[Re: dizuster]
#504031
10/22/09 07:43 PM
10/22/09 07:43 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Quote:
Quote:
Quote:
CNC is repeatable, but can't take advantage of making the port as big as possible because of casting shift.
Why would you want the ports larger on core shifted heads?
That's the point. CNC programs have to work on every single head, even the one's that are core shifted. That means the programs have to be conservative (small) to account for core shift. A hand porter can take advantage of a good casting...
Quote:
Quote:
A good hand porter can feel/hear when the walls are getting thin.
Really?
Now thats a skill I would love to know..Im sure its possible at the point were its almost through the side of the runner...LOL..
But at this point the heads are trashed anyways.
I kid you not, a good head porter can hear when the port wall is getting too thin. You can hear the grinder bit change pitch. I suppose grinding on heads 10 hours a day for 20 years will do that to a guy.
so i guess the head porter that did my heads wasn't listening too good,leaked like a dyke.
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Re: Hand or CNC Head Porting ???
#504032
10/22/09 07:53 PM
10/22/09 07:53 PM
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Joined: Jan 2005
Posts: 3,635
Oakland, MI
dizuster
master
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master
Joined: Jan 2005
Posts: 3,635
Oakland, MI
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Quote:
so i guess the head porter that did my heads wasn't listening too good,leaked like a dyke.
I didn't say your head porter could hear it.
I said a good head porter could hear it... 
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Re: Hand or CNC Head Porting ???
[Re: dizuster]
#504033
10/22/09 07:57 PM
10/22/09 07:57 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Quote:
Quote:
so i guess the head porter that did my heads wasn't listening too good,leaked like a dyke.
I didn't say your head porter could hear it.
I said a good head porter could hear it...
i couldnt have said it any better, only thing your missing is the ex head porter.
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Re: Hand or CNC Head Porting ???
[Re: Dodgeman67]
#504036
10/22/09 08:14 PM
10/22/09 08:14 PM
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Anonymous
Unregistered
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Anonymous
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Quote:
I'm sending my hemi heads to Jeff at Modern. 
smartest thing i've heard today.
i'll be right behind you.
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Re: Hand or CNC Head Porting ???
[Re: Dodgeman67]
#504037
10/22/09 08:22 PM
10/22/09 08:22 PM
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Anonymous
Unregistered
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Anonymous
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it really depends on what your building under the heads that should determine the type of porting you have done.
most CNC programs are a one size fits all and may, or may not be the best type of porting for your application.
for most of the stuff we build, i prefer hand ported heads to max out the combo for the intended purpose. pricing is generally close no matter which type you go with.
also, don't get hung up on advertised flow numbers, especially the peak numbers, as they can be all over the map. advertised numbers sell porting much like phony boloney dyno numbers sell engines. talk to some qualified people to find what's best for your individual application.
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Probably the best of both worlds.
