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1998 Subaru Legacy GT Limited
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Discussion Starter #1
If you're into building EJ22D's, you need to read this closely, because it matters to you, and only 97-99 EJ25D heads will be used in this equation, as the 1996 EJ25D heads have chambers which are too large for the EJ22 bore, and should never be used in this sort of application.

EJ22D Version 1 - EJ25D heads + EJ22E/1 block (14.5cc pistons) = EJ22D V1: N/A w/ EJ222 headgaskets yields 9.3:1cr, but EJ22T head gasket yields 8:5.1.

EJ22D Version 2 - EJ25D heads + EJ22E/2 block (12cc pistons) = EJ22D V2: N/A w/EJ222 head gaskets yields 9.6:1cr, but EJ22T head gasket yields 8.8:1.

EJ22D Version 3 - EJ25D heads + EJ221/2/3 block (3.5cc pistons) = EJ22D V3: N/A w/EJ222 head gasket yields 10.3:1cr, but EJ22T head gasket yields 9.8:1.

EJ22D Version 4 - EJ25D heads + EJ22T block (28cc pistons) = EJ22D V4: EJ222 head gasket yields 7.8:1cr, but EJ22T head gasket yields 7.4:1cr.

There are only FOUR EJ22D variants that can be achieved with 97-99 EJ25D heads and all of the EJ22 blocks in combination form. All 97-99 heads have a 46.6cc (rounded up to 47) clover chamber, and all EJ22's have a 97mm bore, 75mm stroke. I repeat, do NOT use 1996 EJ25D heads. Those are identified as having "16 Valve Quad Cam" on their valve covers.

A long while back, when I first started building these, I originally based my coding off of what Subaru does to its EJ's to keep the identification easy. Example, if you're using EJ20K heads on an EJ22E block, I would call that combo the EJ22K, since the 5th digit identifies the heads in use. Have fun with this knowledge.
 

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Discussion Starter #3
Good to know!
Thanks for noting all of this.
No problem! I've been building these engines for years, so I know how to go about it, especially when it comes to USDM Phase 1 parts. There aren't many combos one can do with Phase 1. If anyone needs the compression ratios to the Phase 1 EJ25 hybrids, I'm in the middle of doing the math and combos now. The finished equations will be up in a bit.
 

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....as the 1996 EJ25D heads have chambers which are too large for the EJ22 bore, and should never be used in this sort of application......
Oh really...

I use 96 heads on a ej22e block, but use the 2.5 head gaskets. I have run up to 25psi on this combo with no head gasket issues. Broken pistons are another story
 

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Discussion Starter #5
Oh really...

I use 96 heads on a ej22e block, but use the 2.5 head gaskets. I have run up to 25psi on this combo with no head gasket issues. Broken pistons are another story
Yeah, that's not a good idea at all. The gaskets must match the bore of the block in the EJ22D hybrids, not the head chambers. Either the head gaskets are at risk from being larger than the bore (I tore apart a hybrid that failed this way), or the pistons themselves are at risk from the mushroom chambers created by that combo.

Also, 1996 heads are highly inefficient. They have large intake ports, but the cams aren't really up to the task of revving as high as they need to, and the exhaust ports are smaller than those found in the more aggressive 1997-1999 25D heads, so they don't get rid of exhaust as efficiently, and build up exhaust gas temperatures fairly quickly.
 

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I dunno if i'd call 320whp at 17psi on a mustang dyno "highly inefficient". But i do have 99 cams in those heads, I'm not sure if theres a difference.
 

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Discussion Starter #8
Next up, we have the Phase 1 EJ25 hybrids, which are easier to figure out. Let me warn any potential builder that the EJ25D engines have 2 different kinds of heads and 3 different kinds of bottom ends. We will start with the HLA 54cc heads. Variant 1 is the 1996 EJ25D, which is the very first EJ25D in existence.

This engine was highly based off of the early EJ20G's, but had the bore and stroke increased, along with domed pistons (8cc) to make up an adequate compression ratio. The engine was then revised in 1997-1998, complete with new SLA heads (directly from the EJ20G/K line of that period) @ 47cc & pistons at 14.5cc, and the 1999 EJ25D brought in the Phase 2 block, but everything else the same, so for this purpose, we will treat the 1999 EJ25D like the 1997-1998 version.

For this purpose, we will refer to the 1996 EJ25D as Variant 1, and the 1997-1999 EJ25D as Variant 2, or V1 and V2, respectively.

That being said, lets get down to business.

EJ25D V1 head/V2 block: = Compression ratio @ 8.8:1 with stock head gasket, but 9:1 with EJ251 head gasket.

EJ25D V2 head/V1 block: = Compression ratio @ 10.5:1 with stock head gasket, but 10.8:1 with EJ251 head gasket.

Any gasket being used should always be of the MLS type.
 

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Discussion Starter #10
I dunno if i'd call 320whp at 17psi on a mustang dyno "highly inefficient". But i do have 99 cams in those heads, I'm not sure if theres a difference.
320whp @ 17psi? This is certainly NOT on 93 octane. I don't use e85 in any equation, as it gives the illusion that internals are stronger than what they really are. That kind of power will most certainly not be made on 93 octane, but let's talk about the exhaust ports for a moment, before explaining why the 97-99 heads are undoubtedly better for operation, let alone as the only heads that should be strictly used for USDM EJ22's.

As I have mentioned before, the 96 exhaust ports are smaller, which probably works out to a quicker spool time in hindsight, but EGT's build quickly due to pressure, and the cams are pretty tame. And I mean WRX tame, maybe more like the EJ20D cams, but without the upper rpm bite. Not just that, the heads are HLA, which in itself, is an inefficient design for top-end operation for too many reasons I can state.

Subaru fixed this issue by widening the exhaust ports, which helps with the intake/exhaust flow operation being much smoother, and the heads were changed to a SLA setup, which allows for more power to be made up top, as well as a little down low. The overall setup contributes to a more efficient engine that can make more power, despite having slightly smaller intake ports.

The 97-99 heads are better in this regard, and it shows even more in the vastly similar EJ20K STi heads, as they are the most aggressive Phase 1 heads to have ever come from of Subaru. Put 20K or 20R cams in a 25D head, de-shroud, and you have the potential for madness. A nice on intake port and regrind would put these in a place only bested by the EJ207 heads.
 

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Discussion Starter #11
1999 was ej253.
Only in the Forester and Impreza RS. In the Legacy GT/Outback/SUS, it was still called the EJ25D, but the block and crank are Phase 2, complete with a 5th position main thrust bearing and 52mm rod journals, as opposed to the 1996-1998 block, which had 3rd position main thrust bearing and 48mm rod journals.
 

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i like the hla heads for the pentroof combustion chamber. all the turbo motors are doin it except the ej20k. and we all know how long that motor lasted.

but ya the 319whp was on e70, on e80 im 23+psi. and slipping a HD feramic clutch kit.

im sure we can both agree though the ej22 was one of subarus best engines. i just like to make it scream
 

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Discussion Starter #13
i like the hla heads for the pentroof combustion chamber. all the turbo motors are doin it except the ej20k. and we all know how long that motor lasted.

but ya the 319whp was on e70, on e80 im 23+psi. and slipping a HD feramic clutch kit.

im sure we can both agree though the ej22 was one of subarus best engines. i just like to make it scream
You drive a good point in this. The pent roof chambers are amazing, so I'm sure that an exhaust porting would put the 96 heads right where they belong. It'd bring down the EGT's and help with flow, too.

As for the EJ20K, they blew up here in the USA because of their aggressive timing maps/fuel trims. EJ20R's and H's followed suit. 93 isn't aggressive enough for them, even with timing control, especially the 9:1 version engines.

The EJ22 was Subaru's sleeping knockout king. They sound positively DIVINE at 8500rpm. Who would have known way back then that this silly little truck engine would be one of our best performance pieces under the right hands? LOL!
 

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I ran my ej20k on the jap ecu and 93 octane fuel for years, even used a powerfc untuned on it the the last couple years. I still have the ej20k block with perfect pistons, rods, bearings, etc. Please stop spreading false information. There was nothing odd or special about my 97 engine and ecu, other than maybe meticulous maintenance. There were people running their mouth constantly about how it wouldn't last, and that I would have to have the powerfc tuned and even run methanol.
 

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Discussion Starter #15
I ran my ej20k on the jap ecu and 93 octane fuel for years, even used a powerfc untuned on it the the last couple years. I still have the ej20k block with perfect pistons, rods, bearings, etc. Please stop spreading false information. There was nothing odd or special about my 97 engine and ecu, other than maybe meticulous maintenance. There were people running their mouth constantly about how it wouldn't last, and that I would have to have the powerfc tuned and even run methanol.
No offense, but that's YOU and maybe a few others, but every single EJ20K or EJ20R I have ever seen run on pump gas has crapped out a rod bearing or a piston. Detonation is what does them in. If what I'm saying about the hybrids is a true thing, you can be sure that I'm speaking the truth about the JDM stuff as well, considering I've also torn into plenty of them. Let's not even talk about the drama shows the 9:1 EJ20's are. It's mind boggling. And don't say that there are EJ20R's and H's out there running on 93 as is and hitting boost daily. This is all factual stuff that is common knowledge.
 

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Discussion Starter #17 (Edited)
Thanks for sharing this info! Would you mind sharing the combos of EJ22s using phase 2 EJ251 SOHC heads!?
No problem. I'll name them off in variants so that it's easier to understand.

Variant 1 - EJ251 heads + 1990-1996 EJ22E block = 8.9:1 with EJ221 head gasket, 8.3:1 with EJ22T head gasket.

Variant 2 - EJ251 heads + 1997-1998 EJ22E block = 9.2:1 with EJ221 head gasket, 8.5:1 with EJ22T head gasket.

Variant 3 - EJ251 heads + EJ221/2/3 block = 10.3:1 with EJ221 head gasket, 9.5:1 with EJ22T head gasket.

Variant 4 - EJ251 heads + EJ22T block = 7.6:1 with EJ221 head gasket, 7.2:1 with EJ22T head gasket.
 

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Discussion Starter #18
And if anyone was wondering, I'll do the 251 heads + EJ25D blocks for the hell of it.

Variant 1 - EJ251 heads + 1996 EJ25D block = 9.4:1 with EJ251 head gasket, 9.2:1 with EJ25D head gasket.

Variant 2 - EJ251 heads + 1997-1999 EJ25D block = 8.7:1 with EJ251 head gaskets, 8.5:1 with EJ25D head gaskets.
 

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EJ22D Version 3 - EJ25D heads + EJ221/2/3 block (3.5cc pistons) = EJ22D V3: N/A w/EJ222 head gasket yields 10.3:1cr, but EJ22T head gasket yields 9.8:1.
typo?


I may just be to tired but I've read this to many times which one is the ej22ez(phase one with updated pistons and single port heads)
 

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Discussion Starter #20
typo?


I may just be to tired but I've read this to many times which one is the ej22ez(phase one with updated pistons and single port heads)
EJ22D Version 2 - EJ25D heads + EJ22E/2 block (12cc pistons) = EJ22D V2: N/A w/EJ222 head gaskets yields 9.6:1cr, but EJ22T head gasket yields 8.8:1.
 
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