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Is it worth CNC GT40X heads 

 

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 Post subject: Is it worth CNC GT40X heads
Posted: Sun Jan 11, 2009 8:04 pm 
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hi guys,

hope your christmas and NYE break was great.

do you think it would be worth CNCing a pair of GT40X alloy heads despite the cost - $1200.

They have been mildly ported, but i didn't get the bowls polished, and the castings were a tad rough.

Obviously CNC is better as you get a better cut, and each bowl and runner is identical, therefore smoother and more effecient power, but is it worth the extra cost?

 

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Posted: Sun Jan 11, 2009 8:35 pm 
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Good value. More importantly match ports to your intake. Aftermarket heads are good, but AFR165s with the current dollar is about $3000.. lol

 

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Posted: Sun Jan 11, 2009 11:07 pm 
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Depends...what do want out of these heads?
Is the $1200 just for the CNC porting?
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Posted: Mon Jan 12, 2009 3:20 pm 
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I jst want to improve on the current head set-up, and clean the bowls up a bit. CNC has a benefit of more efficient head design as each cyl is identical.

the heads are currently on my motor, and it runs fine (185rwkw), but will CNCing the heads be worth cost/time.

Has anyone had similar experience?

the quote i got was from kostecki engine centre, where their CNC machine is currently tooled for GT40 (P,X,Z) type heads

 

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Posted: Mon Jan 12, 2009 6:17 pm 
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I got the quote too from KOstecki and I wouldn't do it for $1500. That is just for the CNC not the remove and reinstall of the heads.

I'd rather get a set of AFR 165s which are already CNC'd and fit them.

My 2 cents.

 

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Posted: Mon Jan 12, 2009 8:49 pm 
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Timmeh wrote:
I'd rather get a set of AFR 165s which are already CNC'd and fit them.


Yeah but with the AUD as it is at the moment, AFR heads arent really worthwhile.

 

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Posted: Mon Jan 12, 2009 9:56 pm 
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What size are the ports after the porting? Do they publish flow sheets? Being Kostecki's I would expect it to be pretty decent...
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Posted: Tue Jan 13, 2009 10:48 am 
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Most of the cost with the NC work is in the programming but if they already have the program and tools for that specific head, then the cost is far more reasonable. Regardless of the finish, the best benefits of NC porting is the consistency of the port shape.

You have to ask yourself what it would cost to finish them off with conventional manual porting and compare that to someone like Kostecki offer with their CNC method.

Besides the point here but it would be good if someone could get their hands on a powerhead NC program and get a heap of junk E7 heads. There would be a pretty good market here for those.
Sorry /on topic

 

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Posted: Tue Jan 13, 2009 3:21 pm 
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xr8ute wrote:
What size are the ports after the porting? Do they publish flow sheets? Being Kostecki's I would expect it to be pretty decent...


I wouldn't expect it.
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Posted: Sat Jan 17, 2009 6:58 pm 
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speaking to other people, and for my particular case, it would not be worth me spending $$ on CNC porting, as my heads already flow OK, so CNC would be marginal.

However, if i would definately do it if i had bare castings again. I spent $700 on hand porting, and would spend an extra $500 on CNCing.

On another subject. the heads i got had a rough finish (mottled) on the surface of bowl. someone said to me this is sometimes better than a smooth polished finish. any truth in this?

 

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Posted: Sat Jan 17, 2009 8:26 pm 
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Yes it is true. The turbulance cause by the 'rougher' finish mixes the fuel and air a little better. I polished my exhaust ports and bowls but I left the inlets with the ground finish.

 

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Posted: Sat Jan 17, 2009 9:37 pm 
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...so you polished the bowls?

the bowls on my heads are the mottled finish.

 

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