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Old 11-26-2009, 11:43 AM   #1
tedsan126
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Default Legacy EJ22 SOHC to DOHC head swap

Im new to this forum and I have some questions about the head swap i am doing. I have an EJ22 and I want to swap the SOHC head i have now for the DOHC heads from a 98' legacy GT. My question now is where can i find the 98' legacy gt DOHC heads that i need.
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Old 11-26-2009, 02:15 PM   #2
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Since you're new.....I'll be easy on you.

Search first....when that fails, ask.

The DOHC heads won't be an easy swap due to intake manifold differences and possibly exhaust manifold differences (dunno cuz you didn't fill out a profile). On top of that, they will lower your compression ratio....making your motor run worse than it might now.

Subarus are not Hondas. DOHC does not conquer all.

[prerequisite phrase] Swap in a WRX motor [/prerequisite phrase]

Jay Storm
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Old 11-26-2009, 02:31 PM   #3
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the intake and exhaust manifolds stay the same, i have already seen these swapped over and driven them when they have had the DOHC swap, and the car ran great;it was much faster than the stock unmodded ej22's. What I need is someone who has the engine so i can buy the heads. That is what's holding me up now. If i never witnessed this swap being made or driven the car after it had been done i would be inclined to agree with you, but i have.
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Old 11-26-2009, 02:46 PM   #4
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The EJ22 is a SOHC motor. The DOHC heads from the EJ25D will bolt right up, and actually work very well. I Expect a 10-15 HP increase in power, with a slight increase in throttle response. Since I already have a few bolt ons, I might be able to see 20 HP, . With this mod I am swapping out reciprocating mass (Mass that travels up and down) for rotating mass, which is much more efficient. I am, however, inceasing rotating mass, which could make the engine decelerate slower. As the EJ22 is now, when you rev the engine and let off the gas the engine will return to idle very quickly. This drop in RPM's might take a bit longer after the DOHC swap, as the extra set of camshafts give the valvetrain more inertia.

To do the DOHC swap, I will need cylinder heads from a 1998 or similar year GT Legacy. Only the GT legacy has the DOHC heads. Back in the day this is what distinguished the base model Legacy from the GT's, nowadays the GT has a turbo.

I need the heads first and foremost. If I can get them with the entire valvetrain already assembled it will be easiest. I will also need a 98 GT DOHC timing belt. I think the ratio with the stock crank timing pulley will be preserved (IE, the pulley's on the DOHC heads are the same diameter as the SOHC heads). I also need to check on the kind of head gaskets to use. The best bet would to have some made, but I'm not sure if I would want to use the EJ22 style, or the EJ25 style, if there is even a difference. I want to stick with the EJ22 intake manifold, since it has all the same electronics as the ECU im using. This is my plan. My question was not how to do it, my question was where can I get these heads
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Old 11-26-2009, 03:13 PM   #5
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Quote:
Originally Posted by tedsan126 View Post
Only the GT legacy has the DOHC heads.
Not true.

Prove me wrong by searching!

P.S. You know... you could just plug in the DOHC engine...
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Old 11-26-2009, 04:39 PM   #6
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if I had money then i wouldnt be messing around with an ej22 motor I would probably be buying a nissan 240 with an r-32 skyline swap in it. but here I sit, i just want the heads, not the whole motor if i can avoid it. And yes you are correct the 1998 legacy gt is not the only one with the DOHC setup, I realize the 97,96 etc.. also have the DOHC heads.

Last edited by tedsan126; 11-26-2009 at 04:48 PM.
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Old 11-26-2009, 05:43 PM   #7
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if you have a phase one EJ22 then the intake minifold will have an offset bolt pattern, the EJ25D heads have an inline bolt pattern, same as all the phase one JDM WRX's.

this is a very common swap on EJ22t's using EJ20G,K,H,R or EJ25D heads. all of witch have a 46cc combustion chanber. but you have to also swap the whole intake manifold also.

we dont know if you have a turbo engine or an N/A engine right now, but if you have a trubo engine with EJ25D heads you will have 7.5:1 compression ratio. if you have an N/A engine you will be up around 9.2:1.

if you use phase II heads the intake will bolt up but the cam sensors are different and your stock ECU will not run them.

here is what you need on Legacy central http://bbs.legacycentral.org/viewtopic.php?t=41848

-=Suberdave=-
www.suberdave.com
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Old 11-26-2009, 06:48 PM   #8
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It's not a turbo
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Old 11-26-2009, 06:54 PM   #9
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pretty sure its phase one
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Old 11-26-2009, 07:36 PM   #10
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hey sorry to bother the thread but i have dual port exhaust.. and was wondering what headers would fit am i unequal length or equal??
i have a 1995 legacy wagon ej22
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Old 11-26-2009, 09:39 PM   #11
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wrx headers will work, you can get them fairly cheap off of ebay. these should work http://cgi.ebay.com/ebaymotors/AMK-G...Q5fAccessories
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Old 11-27-2009, 10:35 PM   #12
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Quote:
Originally Posted by tedsan126 View Post
the intake and exhaust manifolds stay the same, i have already seen these swapped over and driven them when they have had the DOHC swap, and the car ran great;it was much faster than the stock unmodded ej22's. What I need is someone who has the engine so i can buy the heads. That is what's holding me up now. If i never witnessed this swap being made or driven the car after it had been done i would be inclined to agree with you, but i have.
Tell ya what...you can buy the set of heads I have here for $200. You'll have to source cams as mine went out for regrinding cores a long time ago. I don't think you'll get a phase I EJ22 intake manifold to bolt up to it (I have one of those too....) 97 and newer EJ22 exhaust manifolds are singleport design, so you would need a dual port type to bolt up to the EJ25D heads.

A WRX header usually routes the exhaust up over the subframe (cradle) which is not notched on a NA application, so that might be a little difficult too.

Jay
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Old 11-28-2009, 06:29 AM   #13
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Really listen to any and every word of advice Storm has to say. He is the NA small displacement guru of gurus and has spent (too much?) a lot of time going over just about every option there is with the EJ18, Ej22, EJ251's. For the money my advice is as stated. Pick up a Phase 1 2.5 from an Outback, RS, Forester, or LGT and plug it in. There is no modification required just pulling out the old dropping in the 2.5. done. If you want to Frankenstein a block and heads and such do a search for hybrid NA or 2.2L or something cause there are a lot of fun little builds running around. 2.2's with EJ257 internals and Ej257 blocks with Ej22ez internals and everyting in between.
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Old 11-28-2009, 09:56 AM   #14
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What's your location? I have a complete running 96 EJ25 engine for $500. Even has new head gaskets.
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Old 11-28-2009, 11:33 AM   #15
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I looked at some of the prices for the entire EJ25D and i think im gonna just buy the entire engine and swap it in. Seems like its gonna be a pain to do the head swap. Lookin at it on ebay it seems that i can a jdm EJ25D for about 600 bucks. I have a 95' legacy sedan, will this engine be a direct plug in or is it gonna take some serious modifications?
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Old 11-28-2009, 11:38 AM   #16
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[quote=Seraphinwolf;28972292] For the money my advice is as stated. Pick up a Phase 1 2.5 from an Outback, RS, Forester, or LGT and plug it in. There is no modification required just pulling out the old dropping in the 2.5. done.


Yea I think im gonna do that, I was taking a look at this. http://cgi.ebay.com/ebaymotors/95-96...Q5fAccessories

In the end i believe its gonna be the cheapest option, wat do you think?
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Old 11-28-2009, 12:00 PM   #17
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I think that's the best plan as well.

Good luck with it....you'll love the extra power and torque!

Jay
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Old 11-28-2009, 02:37 PM   #18
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hey one more question storm, how difficult is the swap going to be, is it a direct plug in or is it gonna take some modifications
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Old 11-28-2009, 03:43 PM   #19
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If your car has an EGR valve, you need an engine with an EGR valve. Everything else just plugs in. The PS lines are different, but you should be able to just bend them a bit out of the way.
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Old 11-28-2009, 10:46 PM   #20
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The EJ25D will have an EGR already....so that won't be an issue. If your car didnt have one before, plug the hole in the head and make a blockoff plate for the int. manifold. To plug the head, I use the fittings on the EGR tube. Cut it off and tap the fitting for a bolt.

PS lines can be worked around with a little bending. The coil should be the same type, so the plug wires will work. Kingsbourne makes a special wire just for this swap too. Search that term for a PN.

Everything else should plug and play.

Jay
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Old 11-29-2009, 01:23 AM   #21
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It will work, but:

1. you will need a DOHC intake manifold to match the heads and swap your current engine wiring loom onto the DOHC manifold
2. exhaust manifold bolt right up as long as both heads have the dual ports
3. compression ratio will be lower as the SOHC n/a heads have 40cc and the DOHC heads have 46 cc, you can up the compression ratio by using MY99-01 EJ22 pistons (I've done that swap)

Good luck.
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Old 11-29-2009, 12:08 PM   #22
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where were you able to find the heads? and the intake manifold. how hard is the swap? was it worth it, how does ur car ride now
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Old 12-02-2009, 07:26 PM   #23
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This thread is lacking in major details. The most important is that just slapping DOHC heads on an NA ej22 will lower the compression ratio to unusable levels. It will NOT be faster.

However if this is a turbo I think you could use NA pistons with the DOHC heads for a good CR (too lazy to calculate it ATM)
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Old 12-04-2009, 12:58 AM   #24
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I know that the compression ratio will be lowered but i have decided that im not going to do the swap, too many things are going to need to be changed. I am pretty sure that i am going to just do a complete swap. To do the head swap im going to need to change the ecu because it wont run the DOHC setup, i will have to change the intake manifold, I will have to get different pistons and a whole slew of other modifications. The EJ25D is a direct bolt on. but not plug in. the ecu will need to be changed but in the end i think it will be an easier swap. Plus the EJ25D has a stock 30 more horsepower.
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Old 12-04-2009, 07:16 AM   #25
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For what it's worth, my first swap was from a tired 96 Brighton EJ18 with a broken timing belt....to a mildly ported EJ25D using 96 HLA heads and an EJ20G intake manifold. I swapped the engine harness and throttlebody, hacked up the EJ18 fuel rails to bolt to the manifold and blocked off the EGR ports. In one weekend, the car was running with somewhere near 50 more HP than it had the week prior.....on the EJ18 ECU.

Whoever said that a SOHC ECU cannot run a DOHC motor has not tried.

Jay
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