Cant find this thread so im asking SOHC-->DOHC

[03jerzlegacy]

ok so im sure this is posted somewhere but i cant find it. everyone keeps talking about swapping ej22 dohc to Ej25 dohc and it would work so I have an ej25 sohc in my 03 and the bearing spun warping the block so a new engine is a quick way to get it back on the road. I cant seem to find any EJ25s in my area and the EJ25de seems to be cheap and in stock at most junkyards my question is pretty obvious will a DOHC work with my ecu and harness??

[Huffer]

ok so im sure this is posted somewhere but i cant find it. everyone keeps talking about swapping ej22 dohc to Ej25 dohc and it would work so I have an ej25 sohc in my 03 and the bearing spun warping the block so a new engine is a quick way to get it back on the road. I cant seem to find any EJ25s in my area and the EJ25de seems to be cheap and in stock at most junkyards my question is pretty obvious will a DOHC work with my ecu and harness??

"I have an EJ25 SOHC and want to replace it with an EJ25 DOHC - will it work?"

No. Your ECU won't know what to do with the extra two cams.

[03jerzlegacy]

k thats what i figured.but will the harness at least match up if i can get an ecu

[Huffer]

Probably not.
Why? Because your model of car has things in it that earlier cars don't, and likely the pinouts on the ECU won't be the same.

[Piddster]

Its not that it will not know what to do with the extra cams, more that the trigger patterns completely changed. If you swapped cam sprockets, crank timing pully, and possibly sensors, you could make it work. But is not really worth the effort.


If it was a phase 1 motor, there would be no issue with using EJ25D heads.

[Huffer]

That's a good point. If it's just a spun bearing he could take a short block and slap his SOHC heads on it... might bump the compression up a small amount but that could work.

[decke48]

i know this. to make phase II 2.5 sohc heads work on a phase I 2.2/2.5 all you need to do is swap your phase I cam gears (if DOHC head only the intake gear needs to be swaped) to the phase II heads. im pretty sure you could make it work the other way. and take your phase II intake gears and mount them to the phase I dohc heads. the cam sensors are the same 95-09.

[03jerzlegacy]

ok so im confused i was told that the DOHC block was taller then the SOHC block but if i can just swap the block then that would be easiest. now if the compression is bumped up alittle do subaru ecus compensate the difference or will engine management be needed.timing need to be adv/ret or just different octane gas.(dont know to much about subbie ecus)

[Huffer]

If you swap SOHC heads onto a DOHC block, you can just run 89 octane to avoid detonation.

I was in the process of doing this build myself before sanity and life took over.

[decke48]

the ej25d heads have bigger CC cambers then the SOHC phase II's because the DOHC piston sit above the deck a little at TDC. on the SOHC they sit flush with the deck. so if you swapping SOHC to DOHC you loose a little compression. if you got DOHC to SOHC. make sure the HG's are thick enough so the piston doesnt smash into the head

[Huffer]

If you swap SOHC heads onto a DOHC block, you can just run 89 octane to avoid detonation.

I was in the process of doing this build myself before sanity and life took over.

I'm a nincompoop.
I meant to say, swapping DOHC heads on to SOHC shortblock. Thanks decke!

[sexystover]

hey just so you know, if my plans go through i may have a ej25d shortblock for sale soon and im also in jersey

[03jerzlegacy]

thank you guys all very much for your input but i found a SOHC this week and im picking it up sat . it will work well now i can send my heads in for p&p with out losing my car for weeks :smt023 and stage 2 cams yummy :grin:

[RS22b]

Cool!

I was just going to say i will prob have a ej251 in about a week or 2 for sale. I have a car coming in for a complete swap and his motor will be up for sale when we are done.

Good luck and let us know how it turns out.

And im in NJ too ;)

_billy