Questions about 2.2 to 2.5 swap

[badinvestmest#99]

I have a project impreza OBS that I've built for off roading. The ej22 on this thing kicks rump roast and even though it's the phase 2 its still reliable as hell and has never left to die in the mountains. That being said, I'm getting real close to committing to an ej25 swap because i'd like to be able to use freeways again with the big rump roast tires and bumpers i have on this thing. How realistic/easy is it to bolt on ej22 heads to the block of an ej25 and how much horsepower can I gain with this swap? I'm thinking of going with a 2.5 from a 98 forester because they share the same chassis and have the same engine mounts (almost positive). Can I still use the same cams, valves, injectors, timing belt, water pump... blah blah blah from the ej22? Will the headgaskets from the 2.5 fit the heads of the 2.2? Lastly will my ej22 intake manifold bolt right on the the block of an ej25? Will my ecu freak out or would it just be chill with the swap? I'd appreciate any and all contributions. Thanks guys.

[dfoyl]

inb4 the EJ25 haters...

All phase 2 bits will interchange in terms of intake, etc. And yes, engine mounts should be the same. EJ22 (or EJ20) heads on a EJ25 is the easiest way to bump your C/R, but you may need to run a higher grade of gas (I am running 95 RON with a EJ22 using EJ20 heads, but I also have high-comp custom pistons), so if gas prices aren't cheap you may want to reconsider that.

I am also running EJ25 HG's (Cometic C4578-032), but GD (amongst others) swears by the factory EJ25 HG's (I think it's the "777" ?), so I can confirm EJ25 HG's will work on a EJ22.

 

[idosubaru]

4 hours ago, dfoyl said:

inb4 the EJ25 haters...

All phase 2 bits will interchange in terms of intake, etc. And yes, engine mounts should be the same..

 

Original poster take note that says "all Phase 2" but the 1998 Forester you're asking about is a phase 1 so that doesn't answer your question directly, although I think in the end you'll want a Phase II block anyway. 
Correct - engine mounts are a non-issue for Subaru's, they're basically all located identically, you can drop your engine in a 1987 Loyale or 2008 Tribeca if you wanted to and it'll bolt up. 

4 hours ago, dfoyl said:

iI can confirm EJ25 HG's will work on a EJ22.

 

You used an EJ25 HG on an EJ22 block?   The fire ring would be larger in diameter (EJ25 bore) than the cylinder (EJ22 bore). 
Usually the HG matches the bore so the fire ring matches the cylinder diameter. 

4 hours ago, badinvestmest#99 said:

how much horsepower can I gain with this swap?

I'm thinking of going with a 2.5 from a 98 forester

Lastly will my ej22 intake manifold bolt right on the the block of an ej25? Will my ecu freak out or would it just be chill with the swap?

HP estimates are discussed on the board.  190-ish is a commonly thrown around number - but it ends up depending on which block/pistons/heads you use.  GD mentions his preferred combination of heads/pistons elsewhere.  I think he prefers Phase II pistons/blocks. 

1998 forester is a Phase I block.  I'm pretty sure Phase II is the prefered block to use but someone else will mention or you can search it. 

As to manifold and block - the intake manifold doesn't bolt to the block, it bolts to the heads. 

You're going to bolt your heads to an EJ block - and then your intake manifold bolts to your heads - just like right now.  Basically *NOTHING* changes - you're just sliding out the block and pistons and sliding another one underneath all the heads/intake manifold.  So there's really zero questions about how to do it - or if the electronics matter - because it's all easy and nothing different happens nor does anything change. 

Pick a block - bolt your EJ22 heads to it - swap over all your intake manifold, wiring, sensors, etc. 

Interchanging of intakes/heads/blocks - that is depending on Phase I or Phase II. 
Phase I intake manifolds only bolt to Phase I heads. 
Phase II intake manifolds only bolt to Phase II heads. 

But EJ blocks aren't phase dependent so you can bolt any Phase I or II heads (and therefore intake manifolds because those attach to the heads) to any EJ block, phase of the block does not matter. 

Edited September 19, 2018 by idosubaru

[GeneralDisorder]

What year OBS?

[wtdash]

Phase 1 vs Phase 2

 

And search on 'frankenstein' or is that frankenstine?

 

Edited September 19, 2018 by wtdash

[badinvestmest#99]

It’s 98 OBS

[GeneralDisorder]

Then install the complete 2.5. Don't use any of the 2.2 stuff. Waste of time. 

[idosubaru]

12 hours ago, badinvestmest#99 said:

It’s 98 OBS

That's not a Phase II.  But you said it's a Phase II. 

On 9/19/2018 at 4:38 AM, badinvestmest#99 said:

I The ej22 on this thing kicks rump roast and even though it's the phase 2 

Which is it? 

98 OBS is phase I, use the 98 Forester engine (Phase I) as GD said it's plug and play, you'll want the Forester exhaust mainfold as well as it's dual port and the OBS will be single port. 

99 OBS is Phase II get a Phase II EJ25 (Any 00-04 EJ25 or 99 Forester or 99 Impreza RS) and swap it in.  Sometimes you have to swap the drivers side cam sprocket and crank sprocket from the old engine onto the new one but that should be zero work since an engine should be getting new timing gear anyway before install. 

No need for a head swap in either of those, they're both direct bolt in and plug and play. 

Edited September 20, 2018 by idosubaru

[AZ25RS]

You would use your heads, manifold and sensors and bolt straight to the ej25 block. Your timing would use the ej22.

[GeneralDisorder]

1 hour ago, AZ25RS said:

You would use your heads, manifold and sensors and bolt straight to the ej25 block. Your timing would use the ej22.

No. You just use the complete 2.5. Using the 2.2 heads is stupid.