2.5 to 2.2L swaps

[iriejedi]

So I am curious does anyone know about putting the heads and intake from a 2.5L on a 2.2L short block? Year ranges of 2.5L this can work with, reliability of that ej22 type of frankinengine, headgaskets necessary, etc....

[ocei77]

a search would help.

There is a special Cometic HG that is designed for this application. All depends on sohc or dohc 2.5 and the compression ratio you'll end up with and the goal desired.

 

O.

[iriejedi]

Not trying to make a race car, just a dependable 2005 Outback. This one threw a rod so exploring options on using a ej22 shortblock. Doing a search didn't yeild much here for the 2005 2.5L.

Edited April 21, 2017 by iriejedi

[dfoyl]

The EJ25 has a bad rap on here due to early HG designs. The common Frankenmotor upgrade is EJ20/22 heads on an EJ25 to increase compression, while you are heading in the opposite direction which will give you really low compression. The best bet is to find a similar age, phase 2, EH25 block and replace it. The Outback is an overweight pig like almost all modern Subaru's and dropping off 12% of your displacement is going to be noticeable.

[iriejedi]

Ya seems that one needs to develop an adaptor plate to attach to the intake rather than swapping heads to get a ej22 into a later model Outback.

[AdventureSubaru]

Ya seems that one needs to develop an adaptor plate to attach to the intake rather than swapping heads to get a ej22 into a later model Outback.

 

For a phase 1 yes. the 1990-98 EJ22 is the one worth swapping in place of the less reliable phase 1 EJ25 (DOHC) which had more reliability issues on failed head gaskets and rod bearings. Swapping from phase 2 to phase 1 and vice versa is not an easy task.

 

For your application - Phase 2+ the EJ25 is more plentiful, powerful and reliable than Phase 2 Ej22s (Which ended around 2002) If you happened to have a cheap/free phase 2 Ej22 it would be fine to swap. Otherwise there is nothing to gain from swapping one or frankenmotoring one. Stick with stock and move forward.

[iriejedi]

For a phase 1 yes. the 1990-98 EJ22 is the one worth swapping in place of the less reliable phase 1 EJ25 (DOHC) which had more reliability issues on failed head gaskets and rod bearings. Swapping from phase 2 to phase 1 and vice versa is not an easy task.

 

For your application - Phase 2+ the EJ25 is more plentiful, powerful and reliable than Phase 2 Ej22s (Which ended around 2002) If you happened to have a cheap/free phase 2 Ej22 it would be fine to swap. Otherwise there is nothing to gain from swapping one or frankenmotoring one. Stick with stock and move forward.

I don't believe the 2002 ej22 engine has the same wiring harness connectors as the 2005 ej25. Correct me if I'm wrong.

Edited April 21, 2017 by iriejedi

[GeneralDisorder]

I don't believe the 2002 ej22 engine has the same wiring harness connectors as the 2005 ej25. Correct me if I'm wrong.

Being they discontinued the EJ22 after 2001, yes you are correct. 

 

You DO NOT WANT a phase II EJ22. They burn oil and usually die from rod bearing failure, They were only used in base model 99 to 01 Impreza's and 99 only Legacy L. They are more expensive than 251's and are much less reliable. 

 

Just get a good used EJ251 (1999 to 2005) and install the 770 part number head gasket from Subaru. 

 

GD

[AdventureSubaru]

I don't believe the 2002 ej22 engine has the same wiring harness connectors as the 2005 ej25. Correct me if I'm wrong.

 

I believe you are right. The Ej22s of these years still had a Mass air flow vs. MAP on the 2.5s, but thats just my observation.

 

What can be done with the phase 2 EJ22s is an intake manifold swap which was not an option on the Phase 1. You bolt the 2.5 intake manifold to the 2.2 (And swap in a single port Y pipe and drive)

 

As mentioned though, unless you already have a good phase 2 Ej22 laying around there's no benefit to the swap on phase 2s. Usually it goes the other way. When a 2.2 fails in a phase 2 impreza or legacy it is usually replaced with a 2.5

[iriejedi]

AdventureSubaru,

What I do have laying around is a good phase 1 EJ25 from a 1996 Outback that I put a 2.2L in place of. It needed new gaskets and seals. I had a good 2.2L ready to go so instead refreshing that engine I just dropped the 2.2 in it. The block was running strong when it was removed.

 

Can I use this shortblock and put the heads and intake from the 2005 engine which had the blown bottom end on that old 2.5 bottom? Do I need to use special headgaskets since it's a phase 1 short block?

[idosubaru]

I've done that exact swap EJ25 Phase II heads on Phase I block. I forget what gaskets I used but I recall it wasn't widely known, is google that information. Its out there.

 

I think the pistons hit the heads unless a thick gasket is used.

 

You could also consider swapping the Obase II pistons into the phase I block but I don't mess with pistons without a more compelling reason and I think others more versed than I suggest avoiding it as well.

Edited April 23, 2017 by grossgary

[GeneralDisorder]

You must swap pistons from the phase II into the 96 D block. Then you can bolt it up like stock.

 

If you don't the compression will be outrageously high due to the 96 flat top pistons.

 

GD

[iriejedi]

I think the pistons hit the heads unless a thick gasket is used.

I've heard of people doing this personally as well. Is the car you did that swap to still running? I live in Colorado so a higher compression would be nice going through the mtns!

[iriejedi]

You must swap pistons from the phase II into the 96 D block. Then you can bolt it up like stock.

 

If you don't the compression will be outrageously high due to the 96 flat top pistons.

 

GD

To high to be a dependable runner? Higher compression isn't necessarily a bad thing, especially living at 10,000 ft.

 

Swapping pistons requires cracking open the case correct?

Edited April 23, 2017 by iriejedi

[matt167]

my rough math would put it at 11.5:1 compression, a bit extreme.. No need to split the case, there are access holes for the pins.

[GeneralDisorder]

If you like burning holes in the pistons, go for it. 

 

I've been there, done that, have the shirt and the dead pistons to prove it too. 

 

10.5:1 is max on just about any aluminium head engine, running on pump gas, without a super radical camshaft profile to bring down the DCR. And that's pushing it since Subaru engines of the period (and some of the present day) have horrific combustion chamber efficiency. That's why you'll see turbocharged Subaru engines running 15 degrees advance under boost when the same displacement Mitsubishi engines run 4 degrees. Flame front propagation.....

 

GD

Edited April 23, 2017 by GeneralDisorder

[idosubaru]

still running? no idea, it was over a decade ago.

 

i may have used a thick head gasket for all i know to mitigate the issues they're mentioned, I remember looking into it, but I don't recall what I did. there were companies making "thicker" EJ headgaskets which would help with situations like this, bringing the CR back up, though probably not ideal.  if GD works on and does this stuff every day i would listen to what he says, i probably wouldn't do it again unless it was my own car and i didn't care what happened to it...more of an experiment, which I used to do all the time, but do much less of now. 

[GeneralDisorder]

still running? no idea, it was over a decade ago.

 

i may have used a thick head gasket for all i know to mitigate the issues they're mentioned, I remember looking into it, but I don't recall what I did. there were companies making "thicker" EJ headgaskets which would help with situations like this, bringing the CR back up, though probably not ideal.  if GD works on and does this stuff every day i would listen to what he says, i probably wouldn't do it again unless it was my own car and i didn't care what happened to it...more of an experiment, which I used to do all the time, but do much less of now. 

 

Gary - there's a big difference between using a 96 block (flat top pistons) and using a 97 to 99 block. The OP asked about using a 96 block so that's what I was referring to. If you used a 97 to 99 block/pistons then it would be much lower. You had to have used the thicker HG's because if you don't the piston will hit the head. 

 

GD

[iriejedi]

there's a big difference between using a 96 block (flat top pistons) and using a 97 to 99 block. The OP asked about using a 96 block so that's what I was referring to. If you used a 97 to 99 block/pistons then it would be much lower. You had to have used the thicker HG's because if you don't the piston will hit the head.

GD

Interesting, so the 95 and 96 2.5L shortblock has different pistons from the 97 thru 99 shortblocks. Thank you for this insite. Is there other aspects in the phase 1 blocks that make them different (inferior or superior) from each other or the phase 2 shortblocks? I had noticed the 96 valvecovers looked different from the 97 but didn't think much of that. Also with 97 - 99 does one just need thicker headgaskets and their good to go with this type of swap into a later model 2.5? Are the phase 2 shortblocks superior, I sure see a lot of them with broken cases or knocking lower ends where the phase 1 2.5L just seems to mainly have headgasket issues. Edited April 24, 2017 by iriejedi

[idosubaru]

Ahhh got it. no clue what block so probably a later one. 97-99 EJ25D works but 96 doesn't?

[idosubaru]

There are no 95 2.5s in the US.

 

1996 requires premium gas (I imagine related to what GD just said

 

I think 99s have a #5 thrust bearing change.

 

I haven't seen anything to make me think, all things considered, one is more reliable than another in Phase I or Phase II. Phase Is are older which implies more risk for circumstantial reasons.

 

IMO and experience The only way you'd be able to say EJ25D blocks are more reliable than Phase II is if you could guarantee it's never been overheated. Which is hard to do with their propensity to fail under warranty many years ago and how randomly and deceptively they'd overheat. They were exceptionally prone to overheats, multiple overheats, limping a few miles, and multiple repair attempts due to their sneaky initial failure modes. I could buy one with a blown block nearly any day 10-15 years ago. Probably due to overheating. Completely opposite of Phase II which are typically really clear easy and obvious and overheats are easily avoidable. I've never had a shop call me about phase II failures but did in the early 2000's when places couldn't figure out what was going on.

Edited April 24, 2017 by grossgary

[GeneralDisorder]

The 96 block has flat top pistons, about a 10cc larger combustion chamber, and hydraulic lash buckets. It uses a year specific valve cover gasket and spark plug tube seal. 

 

The 97/98 are basically the same They have 10cc smaller chambers, and dished pistons. But retain the #3 thrust of the 96. 

 

99 blocks have the 97/98 pistons but are otherwise a 2000 block in every other way. 52mm rod journals and #5 thrust. 

 

Any of the three can use any of the pistons. Including Phase II (SOHC) flat top 2000 to 2005 pistons which do not crest above deck height at TDC. Thus with these pistons any of the D blocks become 251 blocks for all purposes regarding head and head gasket selection. 

 

So the OP need only swap the pistons along with a new set of rings (NPR is good) from his rod knocked Phase II engine into the 96. He can then bolt the Phase II heads back on (after thorough cleaning and inspection) and it will, in effect, be a stock 251. Just with 48mm rod journals and #3 thrust. Which will decrease it's long term reliability, but no more so than any Phase I 2.2 or 2.5. The 48mm rod journals aren't really a problem but the #3 thrust can be on heavy clutch applications. I have seen a number of #3 thrust failures - usually on 2.2T's but have seen others as well. Never seen a #5 thrust failure due to "natural causes". Seen it only from improper rebuild. 

 

GD

Edited April 24, 2017 by GeneralDisorder

[idosubaru]

Thanks. I owe you drink (or 3) when I make it to Portland.

[iriejedi]

Thanks GD, unfortunately I have more questions.... If the phase 1 has a thicker case but #3 thrust and phase 2 has a weaker case but with a #5 thrust (superior especially for manual tranny's) can one swap the #5 crank into the phase 1 block or will the 48mm rod journels be to small and case major problems?

 

What I've noticed looking around salvage yards in Colorado with ej25's is all the phase 1's tend have less thrown rods (holes in the block) than the phase 2. Those good phase 2 ej251's are also in higher demand (later model so kind of makes sense) and much harder to find as well.

[GeneralDisorder]

There is no difference in "case thickness".

 

You can't swap the cranks - well you can, but the machine work to move the thrust bearing runs about $600 if you can find a machine shop competent enough to do it and/or willing to destroy a fair number of cases to learn how.

 

In any case, DO NOT split the case. If you have not done this before you are SURE to end up with a steaming pile of scrap metal after your attempt. And don't think that any old machine shop can do it either. Seek Subaru specific professional engine builder experience (such as myself) if you want to do a bottom end. It is not a simple process.

 

The primary reason you see thrown rods is due to oil consumption from carbon build up in the piston rings. Leading to low oil conditions and resulting in rod bearing failure from oil starvation. The oil pump sizes on the early 251's didn't help. The legacy models had 7mm pump rotors vs the Impreza at 9mm and the previous generation engines (and 05+) at 10mm.

 

GD

Edited April 25, 2017 by GeneralDisorder