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Old 03-03-2005, 06:43 PM   #1
M3GTR
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V-mounted 40R...what

Default JDM Sti Head vs. wrx head

Hey I am just curious if the jdm sti ver. 7 or 8 is the same volume as the usdm stock wrx heads. I know the usdm sti heads have larger volume compared to wrx ones, and I wanted to be safe in case I plan on switching over to sti heads when I do my swap. Thanks all.

-Nate
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Old 03-03-2005, 11:44 PM   #2
JDM_Scobaru
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usdm things dont even compare to JDM things.
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Old 03-03-2005, 11:51 PM   #3
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V8 are the ultimates for now, best flowing
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Old 03-03-2005, 11:59 PM   #4
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agreed with hyper
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Old 03-04-2005, 01:11 PM   #5
Matt Monson
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DO a search. There was great thread last year on heads with pics and measurements and all that jazz with Kingpin and Sponaugle and many of the serious tuners around here comparing notes on a number of heads...
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Old 03-06-2005, 01:58 PM   #6
M3GTR
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i am not talking about how much the heads flow, I am talking about the actual volume of the combustion chamber. i want to know how much volume each combustion chamber contains as to be sure my compression ratio stays the same.
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Old 03-06-2005, 02:25 PM   #7
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v7 RAC--is 48cc's (factory spec) but jeff sponaugle measured them at 50cc. WRX ones are 52cc's and jeff measured at 51cc.

What setup is this going to be...obviously you have a bunch of other factors to take into account. Hope this helps.
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Old 03-06-2005, 04:46 PM   #8
M3GTR
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my setup is the following: EJ22t bored 20 over, 2.5RS crankshaft, stock wrx length pauter rods, custom dished CP pistons (for 8.5:1 compression i believe). I am debating between cylinder head setups. I can either go with the stock wrx head, ferrea valvetrain, and crower stage 4 cams, or I can go with the sti ver. 7/8 cylinder head, also with crower cams. I am wondering if I do decide to go with the sti cylinder head, how badly it will affect my compressino ratio.
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Old 03-06-2005, 08:19 PM   #9
Soon2Bgreat
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Sounds nice...any reason you didn't opt for 2.5 length rods also since you are doing custom pistons? What comp. ratio are you shooting for?
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Old 03-06-2005, 08:52 PM   #10
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the wrx length rods are only 1.2mm shorter than the 2.5 length rods. There are some benefits to running the longer rod, but it was more convinient to run wrx length rods. Also the benefits will be relatively minimal since the length difference is so small. I am shooting for 8.0 - 8.6:1 compression ratio.
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Old 03-07-2005, 01:41 AM   #11
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Quote:
Originally Posted by M3GTR
my setup is the following: EJ22t bored 20 over, 2.5RS crankshaft, stock wrx length pauter rods, custom dished CP pistons (for 8.5:1 compression i believe). I am debating between cylinder head setups. I can either go with the stock wrx head, ferrea valvetrain, and crower stage 4 cams, or I can go with the sti ver. 7/8 cylinder head, also with crower cams. I am wondering if I do decide to go with the sti cylinder head, how badly it will affect my compressino ratio.
http://forums.nasioc.com/forums/show...light=cam+info

I would just stick with the wrx heads if your going with the cams. Trying to put the crowers in the jdms seems like a waste.
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Old 03-07-2005, 03:09 PM   #12
M3GTR
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what makes you say that, because i cant use avcs?
On a note on the heads. I was told that the wrx heads are 52cc, and the jdm heads are 48cc. If my compression ratio would be 8.5:1 with the wrx heads. My compression ratio would be 8.89:1 with the jdm heads. This is a little high for me. Do I want the upgraded flow of the jdm heads? or do I want more boost and more timing advance out of lesser heads. I am leaning towards the latter.
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Old 03-07-2005, 03:14 PM   #13
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totoherbs, i wish you wouldnt send me a link to a thread with 173 posts, mainly about engine codes, without pointing out a specific area of the thread. I appreciate the help though.
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Old 03-07-2005, 07:24 PM   #14
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Quote:
Originally Posted by M3GTR
what makes you say that, because i cant use avcs?
On a note on the heads. I was told that the wrx heads are 52cc, and the jdm heads are 48cc. If my compression ratio would be 8.5:1 with the wrx heads. My compression ratio would be 8.89:1 with the jdm heads. This is a little high for me. Do I want the upgraded flow of the jdm heads? or do I want more boost and more timing advance out of lesser heads. I am leaning towards the latter.
With a turbo larger ports do not matter that much, all they will do is move your power band over some. The cams will more then make up for the small port wrx heads.

Quote:
totoherbs, i wish you wouldnt send me a link to a thread with 173 posts, mainly about engine codes, without pointing out a specific area of the thread. I appreciate the help though.
Ya, doing your own research sucks huh...
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Old 03-07-2005, 08:16 PM   #15
M3GTR
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i have done plenty of my own research, and yes it does suck
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