BC

By Committee? But why? Because I think that with the honest input from alot of people here on this board, I could really benefit personally.

I have read all over the internet about porting heads, where to do it, what to do, but I have no flowbench. I won't be doing very much, as the first rule is to do no harm, but I think it could be an interesting thread about people's differing opinions.

I also know there are some individuals around us that have alot of personal experiences with 4V heads, even if they are not vocationally related to the auto industry.

So, here are the pics. This is a car that will see alot of boost, but good port design and chamber design is still important.

I have taken several pictures to assist with the discussion, and one specific picture to make sure the Texture of the ports is discussed as well.






INTAKE





FROM CHAMBER:




EXHAUST

BC

And if anyone needs to see pics of specific areas, I can add additional pictures upon request.

123quattro

Just do some smoothing and don't make the intake side mirror finished. I've heard knife edging the area between the two valves is NOT the way to go.

mark kibort

how much harm would be done by just making all the ports smooth, but not going into the dual port area. Kind of a general clean up . maybe just making the entrance and exit ports a little larger.

would it be worth it??


mk

RyanPerrella

I was thinking about what it would cost to have the ports CNC machined.

CNC porting is becoming pretty common on aftermarket heads for US iron. What would it cost to do that for 928's? Its got to be the optimum way for getting more power and an equal flow in all 8 intake ports and exhaust. I imagine you would need to make a 3D model of the heads which maybe difficult but probably not impossible but once you have a single model then you could run the software and see via CFD where the problem areas are and if there is enough material to remove then write a program for all the ports. The initial pair of heads would be where all the work would come in but then once you have the program for the 5 axis machine you can have the ports duplicated and i dont know how a guy with a grinder would do better then using a modern CFD program along with a CNC machine to get the best results.

Not sure what it costs to do a pair of heads on a 5 axis CNC machine, maybe someone could chime in on what that would possibly cost. I think there are allot of people that would spend $1000 for a pair of CNC ported heads on a 15-20K stroker for sure. I think if the results were good on standard 5.0L cars then anyone doing a headgasket would probably have the heads ported as well. I know i would if it got another 30HP, but who knows, it could produce more. I guess you would want to optimize the intake setup then but i think the ultimate in port work would be done with computers using real tech with the Computational Fluid dynamics stuff thats common place in racing now along with the repeatability of the CNC machining doing the actual cutting.

Anyone else looked into this?

Cheburator

My GTS heads are with my machinist who is rebuilding them and installing 968 valves. I asked him about porting and polishing them and he opined that the heads are rather good. Port maching can be done, but he was very impressed with the overall quality of the castings. The guy knows his stuff as he builds 4v and 5v heads for all the local drag racers and has some impressive projects under his belt. I personally will concentrate more on the intake, where there is more to be gained from porting and polishing.

P.S. I am sure someone will come back with some numbers that will prove me wrong

jon928se

Well you did say it was by Committee.

Having been a member of, subject to, and advisor to many committees I can only say two things.

The worst decision all of them made ; "Let's appoint a management consultant"

The only positive decision some of them managed to make (the others made none) ; "F*%k this let's go to the pub" (paraphrased)

When you get an answer that works let me know

toofast928

Local machine shop here quoted me $2000 to CNC intake and exhaust ports on my 16V.

blown 87

I think that is one area that is best left to the pros who haven PROVEN results, or left alone.
The 4 valve heads look good as they are, and with boost, VE is not as critical as it is in a NA application.

Greg Nettles

mark kibort

I say, send the intake manifold out to be extrude hone
and hand port the areas you can reach with a dremel.

thats probably what i am going to do before the 6.5 liter goes in.

by the way, an update of the Holbert/rennlist project is coming soon. Ill let the guys that built her, chime in. From what i can tell, its finished.



Mk

Fabio421

Polish and port match to the gaskets if you are unsure what is best. I know there was some talk of head work done on Scott Mohr's GTS. Maybe there is some info out there regarding that build. Why don't you just ask Greg. I'm kidding Brendon. Don't get all hurty feelings on me.

6.0-928S

Brendan,
Great pics. Are you a proctologist by trade?

Hammer

RyanPerrella

HA HA

BC

I would ask greg. He has a flow bench. But I need that budget for the 5 dollar a second phone calls for other stuff.

Moving on.

BC

No, but I was up close and personal with the heads, so I took some close pics so people could tell me where I should "Start the proceedure"