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Old 04-30-2009, 10:49 PM   #1
Zero92828
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Default 2.5 short block with 2.2 heads?

Ok, so I've been thinking about future performance upgrades I might wanna look into with my 95 impreza. It has a ej22 in it non-turbo single overhead cam. My question is Mostly, would it be beneficial to buy a 2.5 short block and throw the heads from the 2.2 on it? I've heard that if I throw the 2.5 heads on the 2.2, the compressions ratio will go down and all causae the combustion chambers are bigger on those heads. So would the 2.2 heads on a 2.5 be a good idea? Would I need to replace anyting else in the engine for it to work?
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Old 05-01-2009, 02:50 AM   #2
ballitch
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It is just the opposite of what you are thinking. The EJ22 heads on a EJ25 block will give you a 10.8:1 comp. ratio (if using a 96-99 EJ25 block) and a 11.5:1 comp. ratio (if using a 00-04 EJ25 block).

You should search for a thread titled "high compression frankenstein", it has alot of info for you.

This build has been done many times by many people. It is a fun motor, but it basically makes you run premium fuel.

It is basically a plug and play thing as long as you know how to do a timing belt and head gasket job. Just swapping shortblocks basically. Of course cams are a good idea, along with all the seals replaced. If the EJ25 shortblock is low mileage, I would go for it. If it has over 100k miles I would rebuild it.

On the other hand, you could think about making your car faster in the corners than in the straights. Some 16'' or 17'' rims with good tires along with newer suspension components (struts and springs) would make the car alot more fun in the twistys.


~Josh~
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Old 05-01-2009, 03:16 AM   #3
ciper
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Zero92828 : Is your 2.2 a dual exhaust port head? It wouldn't be too difficult to swap an ej25 and use newer heads. In the next couple days I will install a frankenmotor into my 91 Legacy which is a phase 2 EJ25 block with a set of phase 1 DOHC heads and run it with a 93 computer.


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Originally Posted by ballitch View Post
It is just the opposite of what you are thinking. The EJ22 heads on a EJ25 block will give you a 10.8:1 comp. ratio (if using a 96-99 EJ25 block) and a 11.5:1 comp. ratio (if using a 00-04 EJ25 block).
Your information looks right except a minor nitpick, that should read 96-98 EJ25 (phase 1 design) and 99+ EJ25 (phase two design). They are easily distinguished by the number of bolts holding the transmission to the block - four bolts and two pins for phase 1.
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Old 05-01-2009, 10:26 AM   #4
Matt Monson
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Old 05-01-2009, 04:34 PM   #5
Zero92828
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I'm imagining Id wanna port and polish it eventually too, along with maybe some slightly over-sized valves. I'm also betting It would be in my best interest to tune the ECM as well. Possibly a better fuel pump and bigger injectors might be cool too. I definitely wanna do some suspension upgrades too. I'll most likely end up getting slightly bigger rims, new brakes and a nice coil-over set up. My friend just threw some coil-overs into his 04 STI, that thing corners like a beast. some stronger sway bars would probably be in order as well. It would be cool to make my little 95 LX handle just as good as that 04 STI. This car is also like 500 lbs lighter than the STI so I have a slight advantage in weight on that note. My buddy also said he can find the whole drivetrain from an STI for like 5 grand. Anyone know if theres anywhere I can get a cheaper price on that at all? Or is that like a good price? I'm not in any rush to get any of this by the way. I'm flat broke for a while. I'm almost out of school for auto repair, till then I'm flat broke working at a crap job for peanuts.
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Old 05-02-2009, 10:45 AM   #6
Zero92828
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So I just had a thought. Would the transmission I already have bolt right up to a 2.5 block? I'm not sure if the bolt patterns are gonna be the same and everything.
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Old 05-02-2009, 01:21 PM   #7
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Quote:
Originally Posted by Zero92828 View Post
So I just had a thought. Would the transmission I already have bolt right up to a 2.5 block? I'm not sure if the bolt patterns are gonna be the same and everything.
yes..
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Old 05-02-2009, 06:22 PM   #8
Zero92828
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Alright thank you wir.
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