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Old 04-09-2010, 08:03 PM   #1
likeawind
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Default What is the difference between Wrx cylinder heads and Sti heads

I would like to know if the wrx cylinder heads can fit on Sti or what is the difference between them? also how to tell if my sti block needs honing. I had a knock in the engine. Thanks
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Old 04-09-2010, 10:09 PM   #2
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For one thing the cams and valves are different. WRX heads on the STi block has been done many, many times. It is not something that you simply bolt up and run, as I'm sure you already know. I would suggest you talk to your tuner about it. I sincerely hope that you have someone working on your motor that knows motors as the way your question was posed indicates to me that you really should. I mean no offense, so please don't take my comment in that way.
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Old 04-10-2010, 08:42 AM   #3
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^ as he(I'm asuming your a guy ) said you can do this you but should talk to you tuner about it. the heads bolt right up but you need to run sti head gaskets or something similar to have proper compression.
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Old 04-10-2010, 09:11 AM   #4
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Thank you all, my car is getting built at the dealership, after putting the heads on they realized that they are from a Wrx now I have to buy Sti heads.
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Old 04-10-2010, 09:55 AM   #5
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Quote:
Originally Posted by likeawind View Post
Thank you all, my car is getting built at the dealership, after putting the heads on they realized that they are from a Wrx now I have to buy Sti heads.
And an STI ECU and wiring harness, and if it's an '02-'05 WRX an STI intake manifold, throttle body, and pedal assembly.
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Old 04-10-2010, 12:37 PM   #6
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you do NOT "need" to use an sti ecu, wiring harness, intake manifold, throttle body or pedal assembly to use sti heads and shortblock in a wrx. you just dont utilize the AVCS (dont plug them in) and cap the 5 plugs on the ends of the cams and you're all set. IF you have an STi there is no sense in using wrx heads though, so source them and get them, it will be a big downgrade.
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Old 04-10-2010, 12:57 PM   #7
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WRX heads bolt right up to and work on an STI short block. You dont NEED anything else to make it work.

However, you will have slightly higher compression, which isnt a huge deal. And the WRX heads flow a LOT worse than the STI heads, which leads to a weird almost diesel truck type powerband. A ton down low, nothing up top. A set of $700 cams helps with this a lot, but doesnt completely resolve it.

Most people however, would be fine with just doing a set of cams in the WRX heads on the STI shortblock.


Dont listen to the dealership trying to sell you STI heads.
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Old 04-10-2010, 03:06 PM   #8
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2006 WRX 2.5L USDM heads, and 2007 WRX & STI 2.5L USDM heads, have a port in either for the emissions air-pump air-feed system. You can purchase aftermarket block-off plates and OEM gaskets for this.

Block-off plates: http://www.cosworthusa.com/store/pc/...&idproduct=365
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Old 04-10-2010, 07:38 PM   #9
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Ouch $70.

I paid I want to say $19 for my block off plates. If I remember correctly I got KStech block offs.
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Old 04-10-2010, 09:13 PM   #10
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Quote:
Originally Posted by Big-E View Post
2006 WRX 2.5L USDM heads, and 2007 WRX & STI 2.5L USDM heads, have a port in either for the emissions air-pump air-feed system. You can purchase aftermarket block-off plates and OEM gaskets for this.

Block-off plates: http://www.cosworthusa.com/store/pc/...&idproduct=365
I bought 2007 Sti heads from a Nasoic member, they will fit my 2005 sti right!
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Old 04-10-2010, 09:26 PM   #11
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how can I post pictures here, when I click on the image it ask me for a URL.
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Old 04-10-2010, 11:29 PM   #12
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type in the url
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Old 04-12-2010, 05:12 PM   #13
likeawind
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Dealership is saying that 07 sti heads will not fit my 05 sti, are they on crack? I need help please. Thanks
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Old 04-12-2010, 05:22 PM   #14
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Quote:
Originally Posted by likeawind View Post
Dealership is saying that 07 sti heads will not fit my 05 sti, are they on crack? I need help please. Thanks

Dealerships are 100% by the book. Do NOT ask about tuning/custom setups because they will most likely tell you bad information.

If you want your stock subaru repaired to "like new" condition, take it to a dealership.
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Old 04-12-2010, 05:25 PM   #15
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Do I need a air pump delete plate or something to make this work?
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Old 04-12-2010, 06:07 PM   #16
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Quote:
Originally Posted by likeawind View Post
how can I post pictures here, when I click on the image it ask me for a URL.
Quote:
Originally Posted by beanbeanbean View Post
type in the url
Yes, you must have the pictures hosted somewhere else on the Web so you can enter the URL here. You can't just upload a picture to NASIOC.
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Old 04-12-2010, 06:25 PM   #17
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Quote:
Originally Posted by likeawind View Post
Do I need a air pump delete plate or something to make this work?
To make WRX heads work?

No.

To make 07 STI heads work, yes. I paid like $17 bucks for mine lol.


Why do you need heads??? Is there something wrong with yours?
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Old 04-12-2010, 06:36 PM   #18
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Quote:
Originally Posted by Davenow View Post
To make WRX heads work?

No.

To make 07 STI heads work, yes. I paid like $17 bucks for mine lol.


Why do you need heads??? Is there something wrong with yours?
dude where did you buy it? did it through any engine lights?
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Old 04-12-2010, 06:39 PM   #19
likeawind
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My engine got seized and heads went too, so I bought 07 Sti heads but the dealership is saying they are different, I guess I only need the air pump delete plate to make them work, would my car throw any engine lights due to this modification?
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Old 04-12-2010, 06:41 PM   #20
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Quote:
Originally Posted by wagonryan View Post
Dealerships are 100% by the book. Do NOT ask about tuning/custom setups because they will most likely tell you bad information.

If you want your stock subaru repaired to "like new" condition, take it to a dealership.
My car is stuck at the dealership and I see no point to take the car some where else to have it built now.
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Old 04-12-2010, 06:44 PM   #21
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Quote:
Originally Posted by likeawind View Post
My engine got seized and heads went too, so I bought 07 Sti heads but the dealership is saying they are different, I guess I only need the air pump delete plate to make them work, would my car throw any engine lights due to this modification?
Your car wont know you dont have an air pump to throw a code about, because your car didnt come with one.


ACtually, 07 STIs had dual AVCS. That makes it a bit more problematic, but you could just not run the exh avcs I guess.
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Old 04-12-2010, 07:24 PM   #22
likeawind
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Quote:
Originally Posted by Davenow View Post
Your car wont know you dont have an air pump to throw a code about, because your car didnt come with one.


ACtually, 07 STIs had dual AVCS. That makes it a bit more problematic, but you could just not run the exh avcs I guess.
what do you mean by you "could just not run the exh avcs"
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Old 04-12-2010, 07:33 PM   #23
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Wait, what do you have?

You have not filled out your profile, so we have ZERO idea what you drive, so we have no idea what fits what on your car.

At this point I am done helping until you take 30 sec and fill out your profile. We arent f'ing mind readers



Honestly, why not just use your current 05 heads?? Why are you trying to put 07 heads on your 05 motor?

Do you have a WRX? What year?

What motor WAS in it?
What motor are you trying to put in it?


Fill out your profile I wish they would make it a requirement to fill it out within 24 hours of registering or face an IP ban
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Old 04-12-2010, 07:40 PM   #24
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Thank you!




How do they know your STI has WRX heads? Why would it have WRX heads? Was the motor replaced before?

I dont see how WRX heads would have ended up in your STI unless someone swapped in a BIG TIME downgraded motor.


With WRX heads you should have had a check engine light from the AVCS not being hooked up. You should have been down a LOT on hp, but up a good bit on TQ.


You need to find out what is REALLY going on with that car asap. Sounds like someone may have ripped you off when you bought it. Or the dealership is wrong.
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Old 04-12-2010, 07:41 PM   #25
likeawind
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Ok I just update my profile, my 05 Sti engine got seized and the heads were destroyed too, I bought 07 heads not knowing that they are a little different than the 05 heads, the guy I bought heads from told me heads will bolt right on, I found out that I need air pump delete plates to close the air pump port, is that right? do you guys think that mod will throw any engine light? please I need your expertise. Thanks
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