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Old 08-14-2010, 07:11 PM   #1
ONE_1
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Default 98 EJ25DOHC into 99 2.5rs sohc, HALP

okay so i just bought this motor EJ25 DOHC out of a 98 2.5rs. My car is a 99 2.5rs w/ a SOHC EJ25. is it a straight forward swap or am i gonna have to do some wiring??? im feeling lazy and dont wanna search. any help will be appreciated.
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Old 08-14-2010, 10:10 PM   #2
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If it were me, I would try to find someone with a set of SOHC EJ25 heads and trade them for your DOHC EJ25 heads you got with that motor.

You would have to put a new set of HG's on the motor, but it would be plug and play, just make sure to use the headgasket that matches the block. I.E, Phase I EJ25 DOHC HG.





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Old 08-14-2010, 10:28 PM   #3
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will the heads off my motor work? if i use the intake mani and everything else. since my shortblock either spun a bearing or has a rod knock.
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Old 08-14-2010, 10:32 PM   #4
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If you have your stock heads that would be easy. How many miles are on this 98 block? If its less than 50k, you could chance it and use it with new HG's and seals and all that jazz.

The best solution would be to have a Phase II EJ25 block.



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Old 08-14-2010, 11:46 PM   #5
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The other motor has around 60k and was rebuilt by subaru of plano. Thanks for your help
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Old 08-15-2010, 12:49 AM   #6
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I think you'll have issues with the cam and crank timing if you try to run the dohc with a sohc ecu. I'm pretty sure the sprockets are different.
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Old 08-15-2010, 09:53 PM   #7
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It can be done. I've put a SOHC phase 2 motor in a DOHC phase one outback, the timing is the same. Biggest problem is the intake manifold is Not swapable. The Idle Air Controller from the DOHC is NOT compatible with the SOHC. I ended up frying the computer playing with the IAC wires. Your best bet would be to meet me half way in Mobile and swap engines with me. Or you could use the block from the DOHC with thick head gaskets with your SOHC heads. I haven't tried it, but I've read people try the oposite with thin head gaskets frequently since Phase 1 blocks are getting harder to find.
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Old 08-15-2010, 10:40 PM   #8
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well i do have the ecu from the dohc motor. i just wanted a drop in plug n play swap. yea i cant for the life of me find a sohc ej25 locally.
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Old 08-15-2010, 10:46 PM   #9
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Pull the DOHC heads off, put your SOHC heads on the shortblock and drop it in. Sell off the DOHC heads and keep on motoring. It'll be a bit of a hassle to make the EJ25D work with your current ECU and a whole harness swap to run the DOHC ECU is not a worthwhile venture for the amount of work.....unless it was a WRX harness, ECU and motor. That would be a viable and worthy swap.

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Old 08-15-2010, 11:53 PM   #10
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ok so what headgaskets would i need? i feel like such a n00b
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Old 08-16-2010, 03:05 AM   #11
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Or keep the dohc heads by a highcompression block cams for heads and storage second engine. Then when you can find a L model impreza swap in engine and be a n/a beast in that lil car. Other than that like what everyone else said. Swap heads and new stronger HG. Ohh by the way. Welcome to your new hybrid impreza you along with everyone else. Just remember what u have from what in your car when it's time for parts.
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Old 08-16-2010, 02:10 PM   #12
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Quote:
Originally Posted by ONE_1 View Post
ok so what headgaskets would i need? i feel like such a n00b
Use the thick phase I HG designed for the DOHC Ej25. You don't need to worry about it's quality or sealing. It's been redesigned just like the thin ones have. The key is that with a phase I block you want a phase I HG to keep the timing correct. Oh, and your pistons will hit the bottom of your heads at TDC with the thin gasket.
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Old 08-16-2010, 04:39 PM   #13
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Quote:
Originally Posted by VIsubi View Post
Or keep the dohc heads by a highcompression block cams for heads and storage second engine. Then when you can find a L model impreza swap in engine and be a n/a beast in that lil car. Other than that like what everyone else said. Swap heads and new stronger HG. Ohh by the way. Welcome to your new hybrid impreza you along with everyone else. Just remember what u have from what in your car when it's time for parts.
Is this supposed to be incoherent, or was that accidental?
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Old 08-16-2010, 04:55 PM   #14
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^^^ I just skipped that and went straight to Matt's response. Spot on, as usual!!! I forgot to mention that the OP should stick to the EJ25D headgasket due to the unique way the pistons clear the deck at TDC on that model. I, for one, have had to tear down and redo a similar build due to using too thin of gasket on the phase I EJ25D block.

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Old 08-16-2010, 09:05 PM   #15
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. is it a straight forward swap or am i gonna have to do some wiring??? im feeling lazy and dont wanna search. any help will be appreciated.
Is it just me who sees an issue with the above ?

It's like planning on cooking a 6 course formal dinner but being too lazy to buy potatoes..
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Old 08-16-2010, 10:40 PM   #16
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Is it just me who sees an issue with the above ?

It's like planning on cooking a 6 course formal dinner but being too lazy to buy potatoes..
Right. Did you see the join dates and member numbers of the people giving him straight answers? We're from a different era when "do a search" nazis didn't rule the day. There's really no reason to be a dick to people...
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Old 08-17-2010, 12:06 AM   #17
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Okay. So get the head gaskets from the dohc motor. Well thanks and yes I know I left myself open to a search nazi bashing. I actually did a small search and came up w/ nothing. You guys have been a lot of help and its much appreciated. But I may just sell the car as is. I really can't afford to not have a car anymore and I'm stuck on funds till later nxt month. I'm still up in the air
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Old 08-17-2010, 01:51 AM   #18
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ok just so i understand a dohc motor will not swap into a sohc car?even with intake swaps and ecu?
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Old 08-17-2010, 05:20 AM   #19
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Intakes are not swapable. Different size and bolt pattern. Idle Air controler from the DOHC intake will NOT plug into SOHC wiring harness, and no one has gotten it work that I know of. The ECU from the DOHC will work with the SOHC motor, except IAC as stated before. I think SOHC is non egr also so it would be throwing codes. Basicaly the car will run but will idle like crap, probably stall at idle when you turn the A/C on. Now if you took the time for ecu swap and full wiring harness swap it should work. But that's a crazy amount of work, and always the risk you screw it up. Much easier to swap heads keep your intake manifold and wireing stock and have it run like stock.
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Old 08-17-2010, 05:59 AM   #20
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Do yourself a favor. Sell the DOHC engine, and get an SOHC.

It's just easier. Swapping heads is a pain. It doesn't quite work out right anyway. Plus, you end up with a set of heads you can't use anyway.

If you want to go DOHC engine, you can swap ECU and wiring harness. If I were in your shoes, I would probably go that route, but I probably would end up shooting myself after doing that as well, and I know how to read wiring charts.

For simplicity, my advice is to get an SOHC engine and put it in, even though I personally like the DOHC engine soooooo much more than the SOHC (and I've owned both myself).
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Old 08-17-2010, 10:03 AM   #21
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Quote:
Originally Posted by Matt Monson View Post
Right. Did you see the join dates and member numbers of the people giving him straight answers? We're from a different era when "do a search" nazis didn't rule the day. There's really no reason to be a dick to people...
true. sorry.
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Old 08-17-2010, 10:48 AM   #22
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Do yourself a favor. Sell the DOHC engine, and get an SOHC.

It's just easier. Swapping heads is a pain. It doesn't quite work out right anyway. Plus, you end up with a set of heads you can't use anyway.

If you want to go DOHC engine, you can swap ECU and wiring harness. If I were in your shoes, I would probably go that route, but I probably would end up shooting myself after doing that as well, and I know how to read wiring charts.

For simplicity, my advice is to get an SOHC engine and put it in, even though I personally like the DOHC engine soooooo much more than the SOHC (and I've owned both myself).
There lies the problem. I can't (and trust me I've searched) find a sohc motor. Only person that has one lives out in florida and wants to meet halfway and trade me for my dohc enjine. Only problem is I don't have anyway or time to go out there and do it. This car has become more of a headache than I expected. I've always wanted one but now I truly regret buying it.
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Old 08-17-2010, 11:18 AM   #23
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http://forums.nasioc.com/forums/show....php?t=2039729

i can understand the choice, especially if time/tools/motor knowledge in short supply. (same issues i have BTW) wish i had time to help(new wife/new baby)

so swapping heads too much of a hassle?
cant find anyone here in h-town would help?
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Old 08-17-2010, 01:02 PM   #24
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i have a complete sohc motor came out running just has a bent valve due to timing belt snapping. but if ur heads are good i have a block...
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Old 08-17-2010, 04:45 PM   #25
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There lies the problem. I can't (and trust me I've searched) find a sohc motor. Only person that has one lives out in florida and wants to meet halfway and trade me for my dohc enjine. Only problem is I don't have anyway or time to go out there and do it. This car has become more of a headache than I expected. I've always wanted one but now I truly regret buying it.
Get yourself an ECU and harness then. That's the only suggestion I have...

You're going to have a lot of fun pulling your dash and a lot of interior trim stuff putting the harness in.
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