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Old 02-25-2006, 02:12 PM   #1
spdracr00
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Default 2.5 DOHC --> 2.5 SOHC swap. Please Help!

Hey guys/girls I really need some help. I blew the HG on my99legacyoutback. But i got ahold of a 2000RS 2.5 SOHC longblock. I talked with kelly and sean from rallitek and they said the EGR stuff was different on the SOHC motor. So i spent the last few hrs searching the forums and i see tons of info about people swaping 1.8/2.2 heads onto a 2.5shortblock but i cant find the answers i need.
car status is the motor is out. orig 2.5 dohc has 100k on it. newer 2.5 SOHC has 8k on it. so i have a few options. i'm looking for the easiest and cheapest route. so here goes..

#1 has anyone swapped in a 2000+ SOHC long block for a 2.5 DOHC. If so how did you wire it?

#2 if I want to use the sohc shortblock can i use my dohc heads? will this up my compression or leave it about the same.

#3 what about intake and throttle body. do i want to use the old dohc one or can i use the new sohc parts.

#4 I know i need to use my dohc wiring harness. but can i use my old dohc sensors or will i need to splice my harness to use the newer sohc sensors.

thank you. I really need to get my car back on the road soon...

-ben
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Old 02-26-2006, 09:19 AM   #2
Patrick Olsen
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Quote:
Originally Posted by spdracr00
#1 has anyone swapped in a 2000+ SOHC long block for a 2.5 DOHC. If so how did you wire it?
If you go to www.northursalia.com there are ECU pinout diagrams for pretty much every year. Note that the ECU harness connector on the DOHC and SOHC cars isn't even the same shape, so you'll have to do some splicing.

Quote:
Originally Posted by spdracr00
#2 if I want to use the sohc shortblock can i use my dohc heads? will this up my compression or leave it about the same.
Yes. Yes. Check the Normally Aspirated forum, as I know this has been discussed there.

Quote:
Originally Posted by spdracr00
#3 what about intake and throttle body. do i want to use the old dohc one or can i use the new sohc parts.
If you use the SOHC heads, you'll need to use the intake from the SOHC car. If you use the DOHC heads, you'll need to use the DOHC intake. The bolt patterns at the head are not the same.

Quote:
Originally Posted by spdracr00
#4 I know i need to use my dohc wiring harness. but can i use my old dohc sensors or will i need to splice my harness to use the newer sohc sensors.
Depends on which ECU you use.

Pat Olsen
'97 Legacy 2.5GT sedan
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Old 02-26-2006, 12:28 PM   #3
AWDimprezaL
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here is what you do... you take your old DOHC intake manifold off your engine, flip it off to the side of the car, drop in the new sohc long block, bolt up your DOHC intake manifold to the sohc and be done with it...NOT that big of a deal, you are stressing out for no reason!
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Old 02-26-2006, 12:29 PM   #4
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I've checked the N/A forums and all i could find was poeple doing 2.2 or 1.8 to sohc swaps. I'm wondering if i can just use my old wiring harness from the dohc and my old sensors. or am i gonna have to splice the harness. if its just a matter of splicing on sohc plugs for a few of the sensors thats not a huge problem. but i am weak in the splicing dept. I sent out a pm to a guy who swapped a sohc into his 99 forester but he hasnt replied yet. I would love to get in touch with him and find out how he did it.
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Old 02-26-2006, 12:39 PM   #5
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Quote:
Originally Posted by AWDimprezaL
here is what you do... you take your old DOHC intake manifold off your engine, flip it off to the side of the car, drop in the new sohc long block, bolt up your DOHC intake manifold to the sohc and be done with it...NOT that big of a deal, you are stressing out for no reason!
thats what about 1/2 the people have said. and the other half say it wont work that way cause of the sensors. and Rallitek said it wouldnt work either. but i'm at that point i think where i'm just gonna toss it in. and figure out the EGR and stuff later...
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Old 02-26-2006, 01:03 PM   #6
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Quote:
Originally Posted by AWDimprezaL
here is what you do... you take your old DOHC intake manifold off your engine, flip it off to the side of the car, drop in the new sohc long block, bolt up your DOHC intake manifold to the sohc and be done with it...NOT that big of a deal, you are stressing out for no reason!
The manifold won't bolt up. The best way to deal with this is use the new shortblock with the old heads and manifold. You do NOT want to try and rewire your car for a SOHC ECU. Figure 50 hours to do it and $300 or more in electronics and wiring. A set of head gaskets, intake manifold gaskets, and a timing belt will cost you more like $150. And you can sell of those SOHC EJ25 heads for $300 or so when it's all done...
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Old 02-26-2006, 01:13 PM   #7
AWDimprezaL
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the manifold WILL bolt up, almost all subaru manifolds are the same!, ive put 1.8 intakes on 2.5DOHCs 2.5 dohc intakes on 1.8s ect ect
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Old 02-26-2006, 01:55 PM   #8
John*G
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The Heads intakes are all interchangable up until the 2.5 phaseII (SOHC).
I"ve got both sitting in my garage right now to compare.
John
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Old 02-26-2006, 03:29 PM   #9
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Quote:
Originally Posted by AWDimprezaL
the manifold WILL bolt up, almost all subaru manifolds are the same!, ive put 1.8 intakes on 2.5DOHCs 2.5 dohc intakes on 1.8s ect ect
OK, try to put the DOHC 2.5 manifold on a SOHC 2.5, and see how it goes.

There are 3 flavors of Subaru EJ intake manifolds, many are interchagable, but they are definitely not all the same.
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Old 02-26-2006, 05:07 PM   #10
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i was speaking in generalities i know they arent all the same, but most heads share the same bolt pattern
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Old 02-27-2006, 12:46 AM   #11
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Quote:
Originally Posted by AWDimprezaL
i was speaking in generalities i know they arent all the same, but most heads share the same bolt pattern
Thats still not true. There are 3 bolt patterns - not one that most conform to. Thats why you can't put a 99 SOHC manifold on a 98 DOHC head.

Saying that "most heads share the same bolt pattern" is just spreading misinformation.
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Old 02-27-2006, 11:57 AM   #12
Matt Monson
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DO we really have to go all through this again?

EJ18,Ej22 through '94 in Legacies, and EJ22 in Imprezas through '99 and early sohc NA EJ20: offset bolt pattern.

Ej20G from '89, Ej20K, and USDM DOHC Ej25: inline bolt pattern

SOHC Ej25,Ej22 from 95+ Legacy and 00+ Impreza, DOHC Ej25 post '99,Ej205 and Ej207 since '99 and EJ257: modern larger spaced offset pattern

I have the part numbers and applications sitting right in front of me on my desktop and I have 8 manifolds in my garage of all three types of pattern. Now there is one VERY VERY rare exception, and that is a very small number of '99 DOHC Ej25's that got the modern offset bolt pattern. The odds that the thread starter actually has one of these engines is pretty slim, but it is possible, and only he can tell us what he's looking at...
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Old 02-27-2006, 12:00 PM   #13
spdracr00
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Well, i'm gonna end up rebuiding my old dohc block, so its not an issue. but i can take some pics of the manifold just in case you wanna see.
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Old 03-02-2006, 04:49 PM   #14
Patrick Olsen
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Quote:
Originally Posted by AWDimprezaL
i was speaking in generalities i know they arent all the same, but most heads share the same bolt pattern
Yeah, it was obvious you were talking in generalities when you said IN ALL CAPS that "the manifold WILL bolt up".

Pat
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