is sohc intake manifold compatible with dohc?
 

I'm lookin to upgrade my 2.2 to DOHC ..but I'm not sure if I can use the intake manifold on the DOHC heads. Anybody done this before or have any ideas?

hmm ive been wondering this myself. I keep seeying that nice red manifold with out the tgv's and wishing I could get it, but didn't think it could go on a 2.5i

is there any benefit to using DOHC heads on the 2.5i SOHC? will those even work? if so then the headers should work as well (if you have done the switch)

I've heard NA won't have any gains from a generic standpoint. but take that a second hand info, hopefully someone that knows the truth will chime in

Any intake manifold will fit STi-WRX-RS

If you are thinking of doing a head swap that is a hole other question and much more $$$ and work. You would have to get the rite ECU and possibly motor harness for the rite heads . . . AKA If you have DOHC and want to go SOHC you need different ECU. If you have SOHC and want to go DOHC you need a different ECU. If you are are staying same-same just different year maybe a splice job.
What it comes down to is the sensor plug style, # of wires and position they are on the heads. Like cam position sensors-coil packs/plugs ect.
Also the exhaust side ( bolt pattern and flange ) of the heads are different in later year EJ series heads. So you possibly would have to get a different headder and cat ect...

More assumptions here... I assume putting some DOHC heads would increase the potential RPM limit, and with the right cams would work. However, I don't know if the DOHC (ie: STI heads) fit, or if they would increase the compression ratio to make use of the type of cam profiles necessary for higher rpm use. They probably would flow more tho.

Also, I would not use the WRX or STI intake manifold on an N/A motor. They have a significantly smaller plenum, which would probably hinder the performance...

[B]THIS STUFF MAY HELP TOO>>>>?

Q: "Can I put a <insert engine here> into my <insert Subaru here>?"
A: Subaru has a high interchangability rate as far as drivetrain components go. If your car came with an EJ series engine, then any other EJ series engine will "drop" into your chassis. I say "drop" because while they do share the same engine mounts, some other components may be required to change first before the engine can go in. Think Legos.


Q: "What is an 'EJ' series engine?"
A: EJ is the engine code for many Subaru engines. It is thought to have the following definition: E-Engine and J-H4. They are commonly found in the Impreza, Legacy, Liberty (overseas Legacy), Forester, and WRX. The typical naming convention is the engine code followed by the engine size. ie: a 1.8L engine from a 1993 Subaru Impreza is EJ18.


Q: "I have <insert subaru here>, what are my swap options?"
A: Lets go over the model history first:
EJ18: Found in Imprezas from 1993-1997. Rated at 110hp and 120 ft-lbs
EJ22 Phase I: Found in Legacies from 1990-1998 and Imprezas from 1995-1998. Comes rated at 130hp and 137 ft-lbs, 135hp and 140 ft-lbs, or 137hp and 145 ft-lbs.
EJ22 Phase II: Found in Legacies in 1999 and Imprezas from 1999-2001. Rated at 142hp and 149 ft-lbs.
EJ22-T Phase I: Found in Sport Sedan and Touring Wagons (Legacies) from 1990-1994. Turbocharged and non-intercooled. Rated at 160hp and 181 ft-lbs. Closed deck, cast pistons, forged rods, oil squirters: turbo motor. Poor flowing heads.
EJ25 DOHC Phase I: Found in Legacies from 1996-1999, Imprezas in 1998, and Foresters in 1998. Rated at either 155hp and 140 ft-lbs in 1996 or 165hp and 162 ft-lbs in 1997-1999.
EJ25 SOHC Phase II: Found in Legacies from 2000+, Imprezas from 1999+, and Foresters from 1999+. Rated at 165hp and 166 ft-lbs. There was a slight compression ratio change from 1999-2000 where it went from 9.7:1 to 10.0:1.
USDM EJ20: US Domestic Market WRX. Found in 2002+ WRXs. Rated at 227hp and 217 ft-lbs. Turbocharged, intercooled, open deck, and decent heads.
EJ25T DOHC: Available in 2004 in the Forester XT. Rated at 210hp and 235 ft-lbs. Turbocharged, intercooled, VVTi (Variable Valve Timing), and drive by wire.
EJ25T-STi DOHC: Available in 2004 in the WRX STi. Rated at 300hp and 300 ft-lbs. Turbocharged, intercooled, AVCS (Active Valve Control System), drive by wire, intercooler sprayer, and semi-closed design.

There is also a large variety of engines available from the JDM and EDM locales. The EG33 from the SVX and the EZ30 from the new H6 Legacy can also be found, but they are larger and will be more difficult to swap.

With that out of the way, the choices are pretty limitless. As stated previously, since these are all EJ series engines, they will all bolt into any Forester, Impreza, or Legacy. If the recipient car was an NA car and is receiving a turbo motor from a donor car, then swapping in a turbo crossmember is mandatory to clear the turbo up-pipe. A turbo crossmember from the 1990-1994 Legacy is a direct
swap into the old-age Imprezas. A turbo crossmember from a USDM WRX will require shims between the front control arm front bushing and the crossmember. [url]http://forums.nasioc.com/forums/show...hreadid=351399[/url]
Q: "Why can't I just swap in a new engine and leave everything else?"
A: Good news, you can! The structure and strength of the transmission is realtively unchanged since the 1993 Imprezas (not necessarily a good thing). There are some exceptions though: the turbo Legacies had a more uniform metal composition in the gears while the new STi comes with a robust 6-speed. Other than that, the gear strength is almost the same. You can read all about this here: [url]http://forums.nasioc.com/forums/show...hreadid=289335[/url]

that info is wrong for the ej253 (SOHC engine) the 06+ 2.5i's are rated as followed!

173-hp 2.5-liter SUBARU BOXER engine
166 lb-ft of torque at 4,400 rpm


Pre 05 WRX/STI 2.5/2.0 Engines had tumbler Valves, where as the 02+ RS/2.5i's do not! (06+ WRX/STI's do not have tumbler vavles either ;)) so technically speaking a 06+ STI intake manifold should work on any 2.5i.

i don't see why the DOHC manifold would not just bolt right up to the SOHC heads...i doubt you would need anything but the manifold to do this there is no real difference with them...at least that i know of.

now if you were swapping the heads...yes you would need the STi ECU i believe (but wouldn't that be looking for the turbo?) or you could do a splice job and use the 2.5i harness/ecu with a splice to handle the new heads

wrong on many points, SOHC intake manifolds such as 2.5 sohc WILL NOT fit on dohc heads, be them wrx, or n/a, or older SOHC 2.2s, the 2.2 intake manifold WILL fit on a DOHC 2.5 however

Stale, Old, Digging up the dead, but WRONG info is posted here, so it's getting fixed:

Errors fixed in [COLOR="Green"]Green[/COLOR]

A: Lets go over the model history first:
EJ18: Found in Imprezas from 1993-1997. Rated at 110hp and [COLOR="Green"]110 ft-lbs[/COLOR]
EJ22E Phase I: Found in Legacies from 1990-1998 and Imprezas from 1995-1998. Comes rated at 130hp and 137 ft-lbs, 135hp and 140 ft-lbs, or 137hp and 145 ft-lbs.
[COLOR="green"]EJ222 [/COLOR]Phase II: Found in Legacy [COLOR="green"]L and Brighton in 1999 and Impreza L and Outback models [/COLOR]from 1999-2001. Rated at 142hp and 149 ft-lbs.
[COLOR="green"]EJ22T[/COLOR] Phase I: Found in Legacy Sport Sedan [COLOR="green"]1991[/COLOR]-1994 and Legacy Touring Wagons from [COLOR="green"]1992[/COLOR]-1994. Turbocharged and non-intercooled. Rated at 160hp and 181 ft-lbs. Closed deck, cast pistons, forged rods, oil squirters: turbo motor. Poor flowing heads [COLOR="green"]for HP; Fine for Torque[/COLOR].
EJ25 DOHC Phase I/[COLOR="green"]EJ25D[/COLOR]: Found in Legacy [COLOR="green"]GT, Outback and LSi[/COLOR] from 1996-1999, Impreza [COLOR="green"]RS[/COLOR] in 1998, and Foresters in 1998. Rated at either 155hp and 140 ft-lbs in 1996 or 165hp and 162 ft-lbs in 1997-1999. The '99 EJ25D had a Phase II short block, but Phase I DOHC heads and electronics.
EJ25 SOHC Phase II: Found in Legacies from 2000+, Impreza RS from 1999+, and Foresters from 1999+. Rated at 165hp and 166 ft-lbs. There was a slight compression ratio change from 1999-2000 where it went from 9.7:1 to 10.0:1.
USDM [COLOR="green"]EJ205[/COLOR]: US Domestic Market WRX. Found in 2002+ WRXs. Rated at 227hp and 217 ft-lbs. Turbocharged, intercooled, open deck, and decent heads.
[COLOR="green"]EJ255 [/COLOR]DOHC: Available in 2004+ in the Forester XT and Baja Turbo. Rated at 210hp and 235 ft-lbs. Turbocharged, intercooled, [COLOR="green"]AVCS (Active Valve Control System-same as STi)[/COLOR], and drive by wire. [COLOR="green"] The '04-'05 EJ255 was the Same short-block and heads as STi, with a different turbo, exhaust header/Up Pipe, etc. and accessories.[/COLOR]
[COLOR="green"]EJ257-[/COLOR]STi DOHC: Available in 2004 in the WRX STi. Rated at 300hp and 300 ft-lbs. Turbocharged, intercooled, AVCS (Active Valve Control System), drive by wire, intercooler sprayer, and semi-closed design.