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Old 03-08-2006, 06:16 PM   #1
petawabit
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Default jdm v7 heads vs cosworth heads

Debating if it's worth it. Cosworth gave me these flow numbers:

Intake ports:
Cosworth-368 CFMs
05 JDM Sti Spec-C-337 CFMs
USDM sti-316 CFMs

Exhaust ports:
Cosworth-304 CFMs
05 JDM Sti Spec-c-255 CFMs
USDM Sti-235 CFMs

Dog leg::
Cosworth-287 CFMs
05 JDM Sti Spec-c-221 CFMs
USDM Sti-210 CFMs

Looking at both heads, the JDM head ports look larger. Wondering if I would be able to benefit from the cosworth heads. For me to put them on my 2.0, I would have to modify the cosworth heads which I'm not looking forward to. Heads going on a jdm ver7 block with mahle pistons, pauter rods, balanced and micropolished crank. AVCS 272 cams and a gt30r turbo or gt35r turbo. Car is mostly setup for road racing. Cost difference for me is around 1000 over using the JDM heads. Any recommendations? Thanks
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Old 03-08-2006, 06:30 PM   #2
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My recommendation is to have a good "pocket port" and valve job done, and let 'er eat

Cosworth's reputation notwithstanding, I'd wager there are a few folks out there (besides myself) that would make statements such as:

"Huh?"

"Can't see it."

"Not at 28""

and

"What flow bench are they using, and how is it set up?"

I for one, find it hard to believe that ANY Subaru EJ head would flow 368 cfm....period.

For those that would debate it, I'll take wagers. Seriously. Take the cross sectional measurements, curtain area, etc..... I'll plug the numbers into software (that works), and publish the results. Otherwise, I'm calling B.S.

S.



Quote:
Originally Posted by petawabit
Debating if it's worth it. Cosworth gave me these flow numbers:

Intake ports:
Cosworth-368 CFMs
05 JDM Sti Spec-C-337 CFMs
USDM sti-316 CFMs

Exhaust ports:
Cosworth-304 CFMs
05 JDM Sti Spec-c-255 CFMs
USDM Sti-235 CFMs

Dog leg::
Cosworth-287 CFMs
05 JDM Sti Spec-c-221 CFMs
USDM Sti-210 CFMs

Looking at both heads, the JDM head ports look larger. Wondering if I would be able to benefit from the cosworth heads. For me to put them on my 2.0, I would have to modify the cosworth heads which I'm not looking forward to. Heads going on a jdm ver7 block with mahle pistons, pauter rods, balanced and micropolished crank. AVCS 272 cams and a gt30r turbo or gt35r turbo. Car is mostly setup for road racing. Cost difference for me is around 1000 over using the JDM heads. Any recommendations? Thanks
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Old 03-08-2006, 06:33 PM   #3
petawabit
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Default

Quote:
Originally Posted by n2xlr8n
My recommendation is to have a good "pocket port" and valve job done, and let 'er eat

Cosworth's reputation notwithstanding, I'd wager there are a few folks out there (besides myself) that would make statements such as:

"Huh?"

"Can't see it."

"Not at 28""

and

"What flow bench are they using, and how is it set up?"

I for one, find it hard to believe that ANY Subaru EJ head would flow 368 cfm....period.

For those that would debate it, I'll take wagers. Seriously. Take the cross sectional measurements, curtain area, etc..... I'll plug the numbers into software (that works), and publish the results. Otherwise, I'm calling B.S.

S.
Thanks for the insight. I'll try to find out how their flowbench is set up
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Old 03-08-2006, 09:25 PM   #4
Burnout
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There bench readings are NOT from 28", if im not mistaken its 50" or 51". There reasoning is by flowing more air through, smaller flaws will show up making them be able to create a better flowing head. To what ever extent that is, i don't know.
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Old 03-09-2006, 10:13 AM   #5
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I'll say this, then I'm finished (for now)

If Chapman can't get Trey Cobb a "good" CNC program for his heads, then I'd seriously doubt that Cosworth found something noone else did....Larger valves aren't going to do it.

Ask if it's flowed with the stock intake manifold attached.

S.
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Old 03-09-2006, 12:58 PM   #6
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Data from my V7 Large Ported heads. Yes they are the large port version. It's easy to see the difference by just looking at the ports.

Flow at 28" water

Stock they flowed at .400" lift 262cfm intake and 188cfm exhaust
At .400" lift after porting, they flowed 297cfm intake and 243cfm exhaust
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Old 03-11-2006, 02:48 PM   #7
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Are you considering the heads?

I've always wondered how p&p'd USDM STI heads would flow vs. Ver. 7 JDM heads.

Anybody have experience with either or both?
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Old 03-11-2006, 03:51 PM   #8
petawabit
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Quote:
Originally Posted by keaniegenie
Are you considering the heads?

I've always wondered how p&p'd USDM STI heads would flow vs. Ver. 7 JDM heads.

Anybody have experience with either or both?
Yeah, but thinking it might be too much work since I would need to get new pistons and maybe new cams since I have the jdm sti cams and may have to get the US sti cams. The jdm ports look much larger so I wondering if anyone has had any experience with them or if they thought if it was worth the price difference
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Old 03-11-2006, 10:30 PM   #9
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Quote:
Originally Posted by n2xlr8n
I'll say this, then I'm finished (for now)

If Chapman can't get Trey Cobb a "good" CNC program for his heads
what's that all about?
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Old 03-12-2006, 02:48 AM   #10
n2xlr8n
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Quote:
Originally Posted by MeetMrGlock
what's that all about?

Chapman does a portion, if not all of Cobb's CNC porting....but I'd expect you knew that

I'd bet they don't advertise 368 cfm out of a stock casting.

Granted, Chapman's work recently has not been on par with that of the past, but it's still considerably better than most, IMO.

S.
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Old 03-12-2006, 03:05 AM   #11
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Yes definitely ask them what the depression was those numbers numbers were developed on. Flows scale with the pressure so if we know their flow numbers we can convert to industry standard.

Also verify if those numbers are with a valve installed or just the bare head.
Flow numbers without valve lift / diameter and style of valve, info is pretty useless for comparisons purposes.


You should not buy heads based on peak flow, you should have a hard look at the midrange flow numbers because that is where the valve spends most of its time.

Larry
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Old 03-13-2006, 10:57 AM   #12
n2xlr8n
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Quote:
Originally Posted by n2xlr8n
Chapman does a portion, if not all of Cobb's CNC porting....but I'd expect you knew that

I'd bet they don't advertise 368 cfm out of a stock casting.
FWIW....they don't think so, either.

It seems if Cosworth told you 368 cfm, they are doing some creative marketing

S.
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Old 03-13-2006, 04:16 PM   #13
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n2xlr8n How do you figure chapmans work being not on par? They port and fully machine the factory dodge viper heads, ALOT of the Edlebrock heads, and the factory GM performance ecotec heads. They did all the R&D for these projects and offer a superior product that isnt good in your eyes? Could you name someone better or equal?
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Old 03-13-2006, 05:03 PM   #14
n2xlr8n
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Quote:
Originally Posted by 02Toyowrx
n2xlr8n How do you figure chapmans work being not on par? They port and fully machine the factory dodge viper heads, ALOT of the Edlebrock heads, and the factory GM performance ecotec heads. They did all the R&D for these projects and offer a superior product that isnt good in your eyes? Could you name someone better or equal?
I'm not going to debate this in this thread, as this is off-topic. If you'd like to discuss specific examples, PM me, and I'll give you several.

In response to your question:
There is nothing "wrong" with Chapman's work, as they have ported heads I've owned in the past, and I think other than the folks that are "unreachable" in the business, they could do my heads again. I was simply stating that based on observations of their recent R&D (esp on GM performance heads), they left alot of room for the detail work. There are different levels of "satisfaction", I suppose.

S.
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Old 03-18-2006, 07:31 PM   #15
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saw the cosworth heads in person and the ports looked a lot smaller than what I expected. I also remember people making observations that the port lengths are different between the JDM and USDM heads. Still haven't talked to cosworth yet:-(
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Old 08-10-2006, 02:09 PM   #16
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Quote:
Originally Posted by keaniegenie
Are you considering the heads?

I've always wondered how p&p'd USDM STI heads would flow vs. Ver. 7 JDM heads.

Anybody have experience with either or both?
I have a superflow flowbench with all the port analyzing software and pitot tubes if someone wants to send them out...I'm interested too...I'd like to flow EJ205, ver 7, ver 7 spec c, ver 8-9 (standard big port), ver8-9 spec c and usdm sti heads...see what they do from the factory...then I'd like to run all the race heads too, axis, cobb, cosworth...

I'd run them in given lift increments with the valves still installed...that way we can see the usable flow and flow in relation to a give cam profile (what you will really see with a head, valve and a given cam...)
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Old 08-13-2006, 04:23 AM   #17
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omg! - YES please! This could actually be the most information we've gotten from an unbiased 3rd party.

You don't work for Cosworth do you .

Nasa huh?
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Old 08-13-2006, 04:30 AM   #18
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well, I work for NASA via my school and an internship...one of two poor undergrads there...anyhow, I do design work and am basically the TA/run the labs for the motorsports engineering minor available at the school. This includes the IC engines course!! this gives me access to the flowbench, land and sea dyno, shock dyno, scale pads and all kinds of other fun things
my job has perks but is boring as crap...
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Old 08-15-2006, 12:54 AM   #19
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HOly crap, subscribe! Make it happen!
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Old 08-15-2006, 01:03 AM   #20
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I agree, I would love to see it happen.
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Old 08-15-2006, 01:39 AM   #21
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well, I will surely flow a stock wrx head and a usdm sti head when my car and our shop sti get torn down...
if I can get the big port sti head I want (ver8 or ver7 spec c) that will get flowed too...other than those, they will have to be sent out if they want to get flowed.
-Micah
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Old 08-15-2006, 03:19 AM   #22
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I'm definitely interested too as the motor for my new project was going to to be a full tilt EJ22 closed deck with Cosworth heads at a rotated GT40r, whereas now i'm looking at just buying the full v7 Spec C clip and having it shipped over and using that as a starting point.
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Old 08-15-2006, 06:36 AM   #23
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I do it also.I used crawford block and cosworth head with cams.but I have a big problem..
I can not install EJ25 USDM AVCS cam shaft sensor to JDM ECU .They are different .One of has three pins but the cables to go to ECU has two pins.
I opened new topic for this reason but I wrote here again.
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Old 09-05-2006, 08:26 PM   #24
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Quote:
Originally Posted by petawabit View Post
Debating if it's worth it. Cosworth gave me these flow numbers:

Intake ports:
Cosworth-368 CFMs
05 JDM Sti Spec-C-337 CFMs
USDM sti-316 CFMs

Exhaust ports:
Cosworth-304 CFMs
05 JDM Sti Spec-c-255 CFMs
USDM Sti-235 CFMs

Dog leg::
Cosworth-287 CFMs
05 JDM Sti Spec-c-221 CFMs
USDM Sti-210 CFMs

Any recommendations? Thanks

What did you end up going w/?
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Old 09-09-2006, 07:44 AM   #25
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Quote:
Originally Posted by petawabit View Post
Debating if it's worth it. Cosworth gave me these flow numbers:

Intake ports:
Cosworth-368 CFMs
05 JDM Sti Spec-C-337 CFMs
USDM sti-316 CFMs

Exhaust ports:
Cosworth-304 CFMs
05 JDM Sti Spec-c-255 CFMs
USDM Sti-235 CFMs

Dog leg::
Cosworth-287 CFMs
05 JDM Sti Spec-c-221 CFMs
USDM Sti-210 CFMs

I just posted up a thread asking just this!! haha...

The numbers seem to add up to Cosworth's claims of 15% increase in Intake Port Flow & 31% increase in Exhaust Port Flow.
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