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Old 01-19-2005, 08:38 AM   #1
evolutionyz
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Default Swap is complete! Thanks for the help Matt Monson & Storm!

Swap is complete and running like a champ.
Thanks for your help Matt Monson and Storm!!!!!




Hey everyone,

I am new here and this is my first post. This is probably one of the most informative/intelligent forums I've been on. I've been on here the past two days pretty much all day long reading and gathering information. I am having trouble finding someone who has a write-up on what needs to be done to make a Phase II work in a Phase I's spot. I have a 1998 Forester (Manual) with a blown motor and I also have a 2002 Impreza 2.5 motor here with 35k on it. I read about swapping the DOHC heads onto the SOHC block, is this the only way? I have also read about the sensor issues but I can't find the answer to it. The posts on the 1.8 to 2.5 and the 2.2 to 2.5 help, but I am a newbie with Subaru's and I don't want to assume anything, then run into problems. If anyone can point me in the right direction I would be very very happy. Thanks in advance.

Steve G
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Last edited by evolutionyz; 02-17-2005 at 11:46 AM.
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Old 01-19-2005, 09:09 AM   #2
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I haven't done that exact swap, but others sure have. IIRC....the things to look out for are the TB (plugs for IAC/TPS), EGR configuration (or presense thereof), and coil placement/plug wires. I believe you have to carry over the coil from the 98 because of the plug from the ignitor. Maybe keeping the 98 intake manifold wiring harness would make things easier sensor-wise and just swap the TB....

There definately is extensive info for this swap, although usually into a 2.2 or 1.8 donor car.

Hope you find the info you need.
Jay Storm
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Old 01-19-2005, 11:08 AM   #3
Jaxx
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the only thing that comes to mind is the cam sensor
which is what i think you are asking

the cam sensor determins the spark timing. i believe that it work but have no proof
i would swap over all the acessorys and manafolds then use sohc plug wires
and hope the ecu is smart enough to deal with the increased compression
consider running at least mid grade gas
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Old 01-19-2005, 01:51 PM   #4
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Gotta keep the intake manifold with the heads as the boltup is different. The harness on the other hand....should only require tweaking the plugs for the injectors so they attatch (top vs. sidefeed). I seem to remember kingsborne(?) having a PN for custom plug wires that have a 98 coil end and SOHC boots/lengths. It's documented in a couple threads elsewhere. Found it....PN 16-SVI from Kingsborne Wire Werks.
(NASIOC thread# 539677)
I don't recall alot of drama with the cam sensor. It should reach when plugged in. The reading should be the same unless it's providing other data besides cam position.

Jay Storm
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Old 01-19-2005, 08:33 PM   #5
Matt Monson
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Absolutely freaking nothing need to be changed or customized if you use your DOHC heads on the SOHC block. The block doesn't care what kind of heads it has on it. Use your DOHC heads, and your DOHC intake manifold along with engine wiring harness. You will be running 11.4:1 CR and want to run premium, but you will get some free power too.

Ok, one thing needs to change. You need to switch the idler pullies over from the phase I block to the phase II block so the DOHC timing belt routes properly. That's it...

repeat after me. Legarus. Legarus. We play with Legarus
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Old 01-19-2005, 09:53 PM   #6
harvcharg
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Hey some people tell me that i will need to change my fuel grade and some people tell me i dont. What i am doing id putting a 2.5 liter single over head cam block in my 97 legacy. but i am going to use my stock dual over head cam heads. i know it will bump up the compression but will i need to change my gas to a higher grade even if i dont send the heads out to get machined? i am trying to piece a motor together for my mothers car. if it was for me i wouldent care and i would run good gas. but i am on a budget and just trying to make a good motor.

Harvcharg@aol.com
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Old 01-20-2005, 08:28 AM   #7
evolutionyz
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Thank you guys so much, I really appriciate your help. The motor swap will begin next week! I will post progress and take some pics of any problems we run into. Thanks again, This board ROCKS!
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Old 01-20-2005, 11:47 AM   #8
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Quote:
Originally Posted by harvcharg
will i need to change my gas to a higher grade even if i dont send the heads out to get machined?
machined as in decked ??
unless your dooig somthing to decrease compression yes 11.4 is very high for a subaru 91 as minimum
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Old 01-20-2005, 12:24 PM   #9
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You MUST run premium with octane that high. Contact Cometic if it is a concern. They make a thicker than stock HG that will keep you below 11...
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Old 01-20-2005, 01:55 PM   #10
evolutionyz
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Another thing.....this 02 Impreza 2.5 motor was mated to an automatic trans, I am pretty sure it is compatable with my 98 manual trans though right? Also, thanks for the info guys...

Steve
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Old 01-20-2005, 02:27 PM   #11
Matt Monson
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legos. bolt it on up.
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Old 01-21-2005, 08:54 AM   #12
evolutionyz
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So the stock DOHC head on the SOHC block will produce 11.4 compression ratio???? That seems extreme! A bone stock Integra-R is 11.1...

That Cometic head gasket listed for the j25 Legacy is listed as 100mm Bore and .040 MLS, and that will drop it to below 11? Are their headgaskets reliable, well, obviously more reliable than a paper gasket....
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Old 01-21-2005, 01:05 PM   #13
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The .043"(pretorque thickness) C4264HP gasket obviously won't yield 11.4:1. Maybe some math wizards can calculate the ratio for a better idea. The DOHC heads have slightly smaller chambers than the SOHC. That's where alot of the CR increase comes from.

Are they reliable? I think so......I haven't heard of anyone having a gasket failure with Cometic gaskets yet. They claim to be re-usable since the construction is full SS w/no alu or copper layers. I chose to replace mine after running them for just a week before I bent some valves. They still mic out the same as when I bought them......


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Old 01-26-2005, 11:56 AM   #14
evolutionyz
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Does anyone know the thickness of the factory Subaru gasket?
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Old 01-26-2005, 01:06 PM   #15
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.043...
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Old 01-26-2005, 01:47 PM   #16
evolutionyz
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So it's the same as the Cometic gasket? hmm... I guess I'll just go with the new OEM Gasket then...I was just worried about having too high of compression and 92 octane not being enough for it to not ping...I guess we could always throw a step colder plugs in it if that happens..... having over 11-1 compression just seems alittle scary... maybe I am just being a puss but I just spent alot of money on this 02 motor and I don't wanna destroy it yet....
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Old 01-27-2005, 01:45 AM   #17
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Hey....you are what you eat!!!!! :P

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Old 01-27-2005, 09:27 AM   #18
evolutionyz
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haha..... what head set do I order? for the DOHC or the SOHC or are they both the same?
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Old 01-27-2005, 06:37 PM   #19
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Quote:
Originally Posted by Matt Monson
legos. bolt it on up.


Jay Storm
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Old 01-28-2005, 11:11 AM   #20
evolutionyz
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I am liking Subaru's more and more every minute....thanks Storm.

The swap has officially begun, the DOHC motor is out and we pulled the heads off and sent them out to have them machined and new valve seals. I have New plugs, wires, water pump, timing belt, accessory belts, complete Subaru gasket/seal set ($200!!), new Sachs clutch set, fuel filter and air filter... anything else I will need before we get the heads back and put everything back together?

Last edited by evolutionyz; 01-28-2005 at 11:37 AM.
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Old 01-28-2005, 10:56 PM   #21
Storm
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Pull the oil pump for inspection and retighten the back plate using loctite.


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Old 01-28-2005, 11:01 PM   #22
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Old 01-31-2005, 11:19 AM   #23
evolutionyz
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nice, thanks for the link....is a 98 Phase 1 a MY98 then? Does it just go MY98 for a 1998 and MY99 for a 1999, etc...?
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Old 01-31-2005, 11:32 AM   #24
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Pretty much. There are a few instances of Leggies and Foresters getting newer or hybrid motors from the getgo. A visual verification would be necessary at that point.

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Old 02-01-2005, 05:33 PM   #25
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I'll add to this, another question. OK, heres the deal, im going to buy a new short block from the dealer. I have a 98rs that went kaboom. I have 98 heads. now what shortie to get. The goal is long term reliability. being able to use my 98 dohc heads, and being able to use the computer/harness in my 98 impreza. any thoughts
thanks,
jason
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