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Reverse frankenmotor build questions

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From what I understand, the motor I pulled is a somewhat unique one. I did some reading somewhere and learned that the EJ25D from 1999 has phase 2 parts on it (or is a phase 2 motor, I forgot what all it was tbh). Anyway, when I pulled my 5mt for my swap I got the motor and the ECU as well. Turns out it was a 99 Legacy Outback Limited within the affected range for whatever phase 2 crap I was just talking about. The intake manifold is different, some of the clips are different, etc.


My real question here is could I put those heads (EJ25D) on an EJ22 short block? Would it still have headgasket issues with the 2.2 headgaskets? Is there any way to bump the compression back or higher than stock with this setup? I am going back and forth between a frankenmotor for high compression or this build for stock/lower compression. Either way, she will remain a daily driver. No turbo kits or any crap like that, I just want something unique and fun.


The victim in this case is my 98 Legacy Outback with a 5mt swap and basically nothing else done that would make this difficult. I have a basically completed long block from the 99 outback limited torn completely apart in my garage right now, so I need to know what to do and what what block (or heads if I go that route) to get my hands on. If all else fails, I will just slap it back together and keep it as a spare engine.



tl;dr: 2.5 heads on a 2.2 block, or 2.2 heads on a 2.5 block? Which one is more reliable? Which one is easier?

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im not an expert by any means, but I am going to do the 2.5 block with 2.2 heads to get to around 11:1 comp ratio (91+ octane ONLY)

from what I have read doing it the other way around 2.5 heads on 2.2 block drops the compression low enough that without a turbo you will have a neutered dog of an engine, im sure there is a way you can get the comp up higher and make use of the better flowing 2.5 heads but then if you want cam work you have 4 cams to have ground instead of 2, just seems like a lot of extra work for little to no gain over the 2.5 block and 2.2 heads

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I think youre right man. I was just thinking since the 2.2 blocks are near bulletproof i would use that but i might as well throw a port and polish to the best of my abilities on a high compression motor. As for the octane rating, i live around 4900 ft above sea level. I was thinking I would rub e85 (which is actually e70 up here) for the extra octane rating, but with this altitude 91 premium should be fine eh? Plus I really do not want to go through the hassle of upgrading the fuel system for it.


Which 2.2 heads should I be on the lookout for to do a good frankemotor? Also how do I actually tell if I have a phase 2 block? Pretty sure its a phase 1 with p2 manifild but idk


Thanks man


Edit: All this talk of phase one and two crap is null and void. It's a phase one motor. I just went and looked at everything and it's mostly identical to what's in the car now. Thrust bearing on #3, same manifolds, same throttle body... The differences I saw were tiny like a few different vacuum lines here and there and a bolt hole on the intake for the coil is different. I don't think that makes any of the parts that different from each other.

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