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Old 07-25-2010, 12:37 AM   #1
tenchu
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Default EJ25D w/ EJ20K Heads?

Would it work? Is there a quench issue as with an EJ257/EJ20g/k setup?
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Old 07-26-2010, 09:54 AM   #2
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It will work but you won't be gaining much over the stock heads. Plus you'll still need to lower the compression with pistons...
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Old 07-26-2010, 10:16 AM   #3
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The ej25d heads are the same casting as the ej20k heads, once you put in cams and the turbo plumbing, there's not really a difference.
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Old 07-26-2010, 10:23 PM   #4
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I don't have an EJ25D, I have an EJ20G, and a set of EJ20K heads, I want to do an EJ25/EJ20 setup, and I plan on building the block anyways, so I figured the EJ25D would be the cheaper route. You're saying the EJ20K isn't a much better head than the EJ25D heads? Aren't the EJ25D heads SOHC?
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Old 07-26-2010, 10:26 PM   #5
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I'm saying the EJ20K is the same head as the EJ25D

EJ251 is SOHC, not EJ25D
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Old 07-26-2010, 10:41 PM   #6
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Quote:
Originally Posted by Splinter View Post
I'm saying the EJ20K is the same head as the EJ25D

EJ251 is SOHC, not EJ25D
Oooooooh, okay, my misunderstanding, I apologize
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Old 07-27-2010, 05:17 PM   #7
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Quote:
Originally Posted by tenchu View Post
I don't have an EJ25D, I have an EJ20G, and a set of EJ20K heads, I want to do an EJ25/EJ20 setup, and I plan on building the block anyways, so I figured the EJ25D would be the cheaper route. You're saying the EJ20K isn't a much better head than the EJ25D heads? Aren't the EJ25D heads SOHC?

EJ25D heads are the same as EJ20K....

I have ej20g/ej25d hybrid..... Trust me
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Old 07-27-2010, 06:15 PM   #8
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I wasn't doubting anyone, I'm new to the Subaru world, I was mistaken, I thought the ej25d was the usdm sohc engine.

Are there any advantages to running an ej257 block over an ej25d or ej251 when replacing rods and pistons?
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Old 07-27-2010, 08:55 PM   #9
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This information is relevant to my interests.

25D heads are cheap as chips compared to 20K heads.
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Old 07-27-2010, 09:17 PM   #10
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Quote:
Originally Posted by i_c_the_light View Post
This information is relevant to my interests.

25D heads are cheap as chips compared to 20K heads.
I have a set of 20k type RA valves that drop right into the 25d heads if you're interested, cheeeeap
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Old 07-27-2010, 09:27 PM   #11
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Quote:
Originally Posted by i_c_the_light View Post
This information is relevant to my interests.

25D heads are cheap as chips compared to 20K heads.
I have a good set (25D) f/s if you need some. Complete w/ cams and t-belt covers. Only differences are the oil return port on the 25D is closed off. The oil supply is still there but has a plug in it. Some casting marks are different between the G, K, and D but they are the same head, same design, and use the same cam profiles (or unnoticably close).

OP here is the breakdown in a nut shell.

Heads- EJ25D (2.5 DOHC Phase1), EJ20G and EJ20K are all the same head, as are the cams.

WRX/Legacy heads are diff.

STi heads are diff.

SOHC 2.5 heads are diff.

2.2 heads are diff. 2 designs. single port exhaust and dual port exhaust.

Blocks- EJ25D is weakest. 38mm crank journals are the smallest subaru made in the EJ series (all others are 40mm). weak rods, and thin cyl walls. open deck design

EJ20G/K- open deck 2.0L block similar to wrx engine. There was a closed deck EJ20 but I don't know it's name and supposed to be pretty rare.

EJ205 is wrx engine. open deck, but very thick cyl walls. pretty stout.

EJ251 is single cam 2.5 NA motor. I guess it is pretty good because reddevil is making over 400hp on his. but pistons and rods are not stock. open deck.

EJ255- Legacy, WRX, Fozzie, Baja turbo motor. same as STi block but I think it has different stock pistons.

EJ257-STi semi closed deck, good rods, decent pistons.

EJ22"T"- the 22B engine. arguably the strongest block Subaru ever made. Full closed deck, forged crank. Rods are OK, but pistons are junk. Came ONLY in USDM 90-94 Legacy turbo models and 22B impreza.

EJ22- two diff phases but this engine is Subaru's old work horse. Pretty much bullett proof in stock form. Not really worth "looking for" to build up though.

EJ18-The baby EJ. Came in early impreza's and maybe some Legacy's (not sure).

Any EJ head will bolt to any EJ block. You must have the matching intake manifold as the bolt patterns changed with the heads. Use the head gasket that matches the head. So if you are using EJ20G heads on a EJ257, you would use EJ20G head gaskets. (some people might argue though because OMG STi is the
W1nn4R!!).

You need to be careful about which head you use and what cam it has. If your car is running a EJ20G it will not run any other cam except Phase 1 cams unless you have a standalone like a Hydra.

This is info is pretty blan but remains true for the sake of simplicity. There are minor technicalities and a few other engines I left out to K.I.S.S. (keep it simple....). This obviously not a builder intructions manual but more or less a short guide. LOTS of other things go into the build, especially when changing to forged pistons. This is just a little info for you to know in a nut shell what's what.

Last edited by iluvdrt; 07-27-2010 at 09:38 PM.
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Old 07-27-2010, 09:39 PM   #12
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Thanks! So an EJ255 would likely be the best block to buy with the intent of throwing away the stock rods and pistons in exchange for forged?

Also, I thought the EJ20K heads had a different valve design than the EJ20G heads?
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Old 07-27-2010, 09:42 PM   #13
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Quote:
Originally Posted by iluvdrt View Post
I have a good set f/s if you need some. Complete w/ cams and t-belt covers.

OP here is the breakdown in a nut shell.

Heads- EJ25D (2.5 DOHC Phase1), EJ20G and EJ20K are all the same head, as are the cams. Early G heads are different from K heads.

WRX/Legacy heads are diff. The only difference between the TT Legacy heads and the WRX heads is pretty much the extra oil and coolant plumbing for the extra turbo. 20R heads = 20K STi heads.

STi heads are diff.

SOHC 2.5 heads are diff.

2.2 heads are diff. 2 designs. single port exhaust and dual port exhaust.

Blocks- EJ25D is weakest. 38mm crank journals are the smallest subaru made in the EJ series (all others are 40mm). weak rods, and thin cyl walls. open deck design

EJ20G/K- open deck 2.0L block similar to wrx engine. There was a closed deck EJ20 but I don't know it's name and supposed to be pretty rare. That rare closed deck existed as the EJ20G in the Legacy RS, some Legacy GT manual wagons and has been found in the STi-RA as a customer option. This has been covered extensively.

EJ205 is wrx engine. open deck, but very thick cyl walls. pretty stout.

EJ251 is single cam 2.5 NA motor. I guess it is pretty good because reddevil is making over 400hp on his. but pistons and rods are not stock. open deck.

EJ255- Legacy, WRX, Fozzie, Baja turbo motor. same as STi block but I think it has different stock pistons.

EJ257-STi semi closed deck, good rods, decent pistons.

EJ22"T"- the 22B engine. arguably the strongest block Subaru ever made. Full closed deck, forged crank. Rods are OK, but pistons are junk. Came ONLY in USDM 90-94 Legacy turbo models and 22B impreza. Not even! For starters, the longblock in the 22B is DOHC, the long block in USDM Legacy is SOHC. The two have little in common.

EJ22- two diff phases but this engine is Subaru's old work horse. Pretty much bullett proof in stock form. Not really worth "looking for" to build up though.They are for sure worth looking for. Slap DOHC heads on them and go nuts!

EJ18-The baby EJ. Came in early impreza's and maybe some Legacy's (not sure). They get smaller than that. EJ15, anyone?

Any EJ head will bolt to any EJ block. You must have the matching intake manifold as the bolt patterns changed with the heads. The intake bolt pattern only becomes and issue when going between different phases.

You need to be careful about which head you use and what cam it has. If your car is running a EJ20G it will not run any other cam except Phase 1 cams unless you have a standalone like a Hydra.

This is info is pretty blan but remains true for the sake of simplicity. There are minor technicalities and a few other engines I left out to K.I.S.S. (keep it simple....).
I'll pass on all offers, I've got other priorities right now. But the head info is good for future reference.
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Old 07-27-2010, 09:45 PM   #14
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To clarify, the ej20g/20k/25d use the same DESIGN cam, but they are not the same grind.
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Old 07-27-2010, 09:57 PM   #15
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Quote:
Originally Posted by Splinter View Post
To clarify, the ej20g/20k/25d use the same DESIGN cam, but they are not the same grind.
I planned on running re-ground or aftermarket cams, so the cam design isn't really important to me. But it would be **** if I bought EJ20K heads and they are exactly the same as my EJ20G heads I already have. But I was told the valve design was better for more rev's on the EJ20K
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Old 07-27-2010, 09:59 PM   #16
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Quote:
Originally Posted by i_c_the_light View Post
Early G heads are different from K heads.

In what ways? I have taken apart a V2. 20G and it was almost identicle to the EJ25D heads. Cam profiles were the same as well.

The only difference between the TT Legacy heads and the WRX heads is pretty much the extra oil and coolant plumbing for the extra turbo. 20R heads = 20K STi heads.

I meant different from the phase 1 heads. My bad for not clairifying.

That rare closed deck existed as the EJ20G in the Legacy RS, some Legacy GT manual wagons and has been found in the STi-RA as a customer option. This has been covered extensively.

Good to know, I couldn't remember but knoew it was covered. Also that is not to say ALL 20G's were closed deck, only those particular ones.

Not even! For starters, the longblock in the 22B is DOHC, the long block in USDM Legacy is SOHC. The two have little in common.

LOL, I was talking about just the block halves. No one can confuse a USDM EJ22 with a 22B EJ22. I was only talking about the block its self, not the whole engine.

They are for sure worth looking for. Slap DOHC heads on them and go nuts!

I am not even getting into this debate again. I agree they make a good engine, but a lot of others dont so I am leaving this one open to discussion....

They get smaller than that. EJ15, anyone?


Had no idea. Is it a USDM engine??

The intake bolt pattern only becomes and issue when going between different phases.

Right. As did the cam triggers, cam designs, and a lot of other stupid small things that make hybrids "fun" to build. all the little differences LOL.


I'll pass on all offers, I've got other priorities right now. But the head info is good for future reference.
Thanks for clairifying a few Things. I was trying to hurry a bit and not get too technical.

Quote:
Originally Posted by Splinter View Post
To clarify, the ej20g/20k/25d use the same DESIGN cam, but they are not the same grind.
There isn't a huge difference, and they are not really worth sourcing out. I have measured EJ25D cams with open deck EJ20G cams and at least the lift was the same. IDK about duration or the K's, but they appear to be the same as well.

I asked in a thread a couple months ago about this same question. Matt Monsoon stated there were no real differences. I measured them with a digital micrometer and he was right. I can find and post the thread link if anyone wants it.

Last edited by iluvdrt; 07-27-2010 at 10:05 PM.
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Old 07-27-2010, 10:04 PM   #17
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Quote:
Originally Posted by tenchu View Post
I planned on running re-ground or aftermarket cams, so the cam design isn't really important to me. But it would be **** if I bought EJ20K heads and they are exactly the same as my EJ20G heads I already have. But I was told the valve design was better for more rev's on the EJ20K
On the type RA ej20ks it's shim under bucket, which is better. but the regular STIs use shim over bucket, same as the USDM

The duration is what's important between N/A and turbo, and they're different.

early EJ20Gs were hydraulic lifter, entirely different.

Oh and the 22B engine is a phase 2 engine, so the thrust bearing is in the #5 position, the usdm ej22t is phase 1.
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Old 07-27-2010, 10:07 PM   #18
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Quote:
Originally Posted by tenchu View Post
I planned on running re-ground or aftermarket cams, so the cam design isn't really important to me. But it would be **** if I bought EJ20K heads and they are exactly the same as my EJ20G heads I already have. But I was told the valve design was better for more rev's on the EJ20K
Well the lifter designs changed from HLA to shim over bucket designs. The non-shimmed designs are better I guess. I have heard people say they have made the shims pop out before. That isnt really a difference in the head though, just some of its hardware....which is interchangable.
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Old 07-27-2010, 10:11 PM   #19
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HLA was what I was trying to think of (its been quite some time since I did any head research after I bought my 20K heads). From why I hear HLA's like to float above 7k rpm. I'm looking to run a fairly large turbo, hence why I need the added displacement and extra revs
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Old 07-27-2010, 10:11 PM   #20
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Quote:
Originally Posted by Splinter View Post
On the type RA ej20ks it's shim under bucket, which is better. but the regular STIs use shim over bucket, same as the USDM

The duration is what's important between N/A and turbo, and they're different.

early EJ20Gs were hydraulic lifter, entirely different.

Oh and the 22B engine is a phase 2 engine, so the thrust bearing is in the #5 position, the usdm ej22t is phase 1.

I wasn't sure about duration. GTK!

I also wasn't sure about the 22B thrust.

When is the date line for early 20G's and late 20G's? Both the 20G's I have worked with were shim over bucket and open deck.
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Old 07-27-2010, 10:12 PM   #21
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What turbo?

I'm running a 20G on my 2.2L block w/ modified 25D heads
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Old 07-27-2010, 10:13 PM   #22
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Quote:
Originally Posted by iluvdrt View Post
I wasn't sure about duration. GTK!

I also wasn't sure about the 22B thrust.

When is the date line for early 20G's and late 20G's? Both the 20G's I have worked with were shim over bucket and open deck.
I just sold a 1989 ej20g with closed deck and HLA

I think all the imprezas came with solid lifters but the 89-92 legacys overseas came with open deck HLA ej20gs
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Old 07-27-2010, 10:22 PM   #23
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Quote:
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I just sold a 1989 ej20g with closed deck and HLA

I think all the imprezas came with solid lifters but the 89-92 legacys overseas came with open deck HLA ej20gs
Gotcha. I was working with a RHD JDM swapped 95 Impreza. Thats why. IDK what car either of the motors out of but both were def EJ20G's, open deck and had shim over bucket. I actually think the one we swapped in to replace the blown one was a 20G w/ a 20K manifold. The IAC valve was slightly different and IIRC the TPS was too. (4 wire vs 3) Head casting hatch marks were identicle and they both had the shim over bucket....which is why I think it had a diffferent manifold on it.
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Old 07-27-2010, 10:29 PM   #24
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Quote:
Originally Posted by Splinter View Post
What turbo?

I'm running a 20G on my 2.2L block w/ modified 25D heads
GT35/GT40 area. But not Garrett. Don't have a set turbo in mind yet, still working on collecting all the parts to support it.
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Old 07-27-2010, 10:29 PM   #25
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I've only had 2 JDM motors in my personal possession
1989 Legacy RS-RA (Closed deck, HLA)
1998 STI Type RA (Open deck, shim under bucket)

I've worked on a few 92-93 WRXs but never had the motors apart.
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