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Old 04-23-2009, 02:38 PM   #1
sniper512
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Default Early EJ20G heads with 2.5 STI Block?

I was just wondering if this is possible. I have a 93 JDM WRX. I am going with the STI 6MT as well. I wanna use my heads and everything else in the car except swap in a 2.5 block and 6MT for more power handling and reliability.

I will most likely be going standalone down the road.
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Old 04-23-2009, 04:03 PM   #2
Matt Monson
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Yep. It's been done a bunch of times. It's a bolt on affair. The only additional challenge is the extra crankcase breather and the coolant crossover pipe. But it's not a major issue.
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Old 04-23-2009, 11:27 PM   #3
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So basically a good catch can setup and a modified pipe. Hmm well I'll start looking. A stock short block seems fairly inexpensive. The tranny will be the biggest cost. At least with the sti block the 6MT will bolt up with all 8 bolts not 4 lol.

So the oil and coolant journals are the same between the 2.5 block and the older phase 1 ej20g's?
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Old 04-24-2009, 01:24 AM   #4
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Yeah.
Beware if those are the rocker EJ20G heads, lifter suck and they make no power up top.
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Old 04-24-2009, 04:45 AM   #5
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In the first post it says 93 JDM WRX so it won't have the rocker heads.

Be aware that compression ratio will be as follows:

9.2:1 with 0.58mm original EJ257 gasket 11044AA641 (holes for intake manifold won't line up)
8.9:1 with 1.00mm Cometic gasket
8.6:1 with 1.37mm original EJ25D gasket 11044AA610
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Old 04-24-2009, 10:41 AM   #6
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So the EJ257 from the USDM STI isn't gonna work with my intake mani?

EJ25D what car has this motor and how much power is it able to hand roughly?
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Old 04-24-2009, 10:54 AM   #7
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That's not what he's saying. The Ej257 will work, but you just want to use the Ej25D (dohc NA engine from 1996-1999) gasket. It's a phase I gasket and is thicker, which is what you want since you are using phase I heads. It's both the right compression ratio and the right manifold spacing. You just need the gasket, not the block.
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Old 04-24-2009, 11:55 AM   #8
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Haha oops ya that makes sense. Thanks for the help. I'll start sourcing parts for this. One other question though. Do you think the factory ECU will be happy with the extra displacement? I would imagine so. It would only be temporary till I got a standalone.
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Old 04-24-2009, 05:39 PM   #9
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Quote:
Originally Posted by Matt Monson View Post
That's not what he's saying. The Ej257 will work, but you just want to use the Ej25D (dohc NA engine from 1996-1999) gasket. It's a phase I gasket and is thicker, which is what you want since you are using phase I heads. It's both the right compression ratio and the right manifold spacing. You just need the gasket, not the block.
I have used the 257 HG on a EJ257/EJ25D build, intake manifold fit/lined up fine.
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Old 04-24-2009, 06:47 PM   #10
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Quote:
Originally Posted by DSM_Outback View Post
I have used the 257 HG on a EJ257/EJ25D build, intake manifold fit/lined up fine.
Talk to Marnix about it. I wasn't the one making the claim. I just re-explained to the OP what Marnix was telling him to do. I've never built this particular motor.
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Old 04-24-2009, 07:06 PM   #11
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Quote:
Originally Posted by sniper512 View Post
Do you think the factory ECU will be happy with the extra displacement? I would imagine so. It would only be temporary till I got a standalone.
Thats a big fat NO. you are looking at 25% more displacememt. you will need a way of tuneing and you will need much larger injectors.

i spent my money on EM first. now i can do anything i want, and be able to tune for it...

-=Suberdave=-
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Old 04-24-2009, 07:20 PM   #12
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+1 for suberdave!
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Old 04-24-2009, 08:34 PM   #13
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That's what I will do. I am just going to start finding what I need for next winter no big rush. For this summer I'll be happy with 250whp+ i suppose lol. Next year I'll build her up when my shop isn't so busy.
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Old 04-25-2009, 01:46 AM   #14
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Quote:
Originally Posted by DSM_Outback View Post
I have used the 257 HG on a EJ257/EJ25D build, intake manifold fit/lined up fine.
The block will be roughly 2 mm less wide with the thin gaskets therefore the manifold won't line up. You can drill out the holes in the manifold though to make it work but why would you want to do so if you end up with a too high CR anyway? Besides, the ports of manifold to head will also be off (by 1mm per side).

Besides those issues you will also have to use the latest belt tensioner setup with the extra idler when using the thin gaskets to prevent belt slack. With the thicker gaskets you can use your original setup.

As for the EM: I agree with Dave, fully. However, you can use the original ECU temporarily but you will have to run waste gate pressure (ca. 0.4-0.5 bar) only to prevent the issues described.
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Old 04-25-2009, 01:56 AM   #15
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Awesome thanks for all your guys help.
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Old 04-27-2009, 01:01 AM   #16
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Quote:
Originally Posted by Marnix View Post
The block will be roughly 2 mm less wide with the thin gaskets therefore the manifold won't line up. You can drill out the holes in the manifold though to make it work but why would you want to do so if you end up with a too high CR anyway? Besides, the ports of manifold to head will also be off (by 1mm per side).

Besides those issues you will also have to use the latest belt tensioner setup with the extra idler when using the thin gaskets to prevent belt slack. With the thicker gaskets you can use your original setup.
I agree on the tensioner setup but continue to disagree with you about the manifold geometry.
This build I did was for a US 98 Legacy GT, it had an EJ25D in it. We ditched the shortblock for an EJ257, I rebuilt the heads and we used EJ257 OEM STI headgaskets and I 5hit you not, intake manifold installation was smooth. No hogging holes out or drill bit wiggling was required. True story.
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Old 04-27-2009, 10:08 PM   #17
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Quote:
Originally Posted by Marnix View Post
In the first post it says 93 JDM WRX so it won't have the rocker heads.

Be aware that compression ratio will be as follows:

9.2:1 with 0.58mm original EJ257 gasket 11044AA641 (holes for intake manifold won't line up)
8.9:1 with 1.00mm Cometic gasket
8.6:1 with 1.37mm original EJ25D gasket 11044AA610
what would be ideal. im thinking about ditching my ej20k shortblock for a 257 as well
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Old 04-28-2009, 12:17 AM   #18
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Quote:
Originally Posted by Marnix View Post


9.2:1 with 0.58mm original EJ257 gasket 11044AA641 (holes for intake manifold won't line up)
8.9:1 with 1.00mm Cometic gasket
8.6:1 with 1.52mm original EJ25D gasket 11044AA610
Take that into account.


~Josh~
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Old 04-28-2009, 12:17 AM   #19
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Below 9:1 on pump gas, on E85 the higher the better IMO.
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Old 05-07-2009, 07:10 PM   #20
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Quote:
Originally Posted by Marnix View Post

Besides those issues you will also have to use the latest belt tensioner setup with the extra idler when using the thin gaskets to prevent belt slack. With the thicker gaskets you can use your original setup.
Marnix which one is the latest? The one piece with one bolt and the whole thing pivots or the two bolt holding the cylinder and seperate pivoting pulley? Is this a straight forward bolt on affair to switch between both? I've had both apart but can't remember.
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Old 05-07-2009, 10:37 PM   #21
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One bolt is the newest and you'd need the mounting bracket as well.
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Old 05-09-2009, 03:40 PM   #22
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Well, since it looks like the original poster had his questions answer I'm going to take over, lol. I'm trying to cost out doing this swap and figuring out everything that is needed to make this go smoothly (if anyone does this in the future). If I do go ahead with this swap I'll update with any additional things I run into. Here are two other threads discussion this: STI Block EJ20G heads? and Ej20g + Ej257 = ?

My car has 550cc injectors, TD05-16g and using Apexi PFC for tune. I'm looking for around 350 hp atc. I imagine I'll be upgraded the MAF to a Z32 or Q45. If anyone can add to this list with numbers and any other parts needed I will update it with your posts to help make this an easy conversion for those in the future.

New parts needed

-Ej257 short block - 10103AB440
-Ej257 oil pump - 15010AA280
-Ej257 water pump - 21111AA240
-EJ257 timing belt - 13028AA240 if switching to new style tensioner
-EJ257 tensioner, mounting plate and extra idler -
I've also read that you can use the old style tensioner but not sure which belt you'd use then?
-Head gasket -
if early legacy heads use EJ257 - 11044AA641
if wrx heads use EJ25D - 11044AA610
-Head bolts
-Gasket kit - not sure whats all included - intake mani, exh,?


Also I would change (part numbers needed, not sure in differences between wrx and legacy heads here)

-EJ20g cam seals - 806732150
-Ej20g Valve Cover seals - are these needed or can they be cleaned and work like new?

Last edited by Eatoniashoprat; 05-10-2009 at 09:11 AM.
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Old 05-09-2009, 05:55 PM   #23
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Sorry to hijack but since were on the discussion of headgaskets to use with different block/heads. I am doing an ej25d block with ej18 heads from my 93 L. I was told that it will be a bolt on affair also. But I am curious as to what headgaskets to use? I think ej257 gaskets would be best. But I also want to raise the compression as this will be an all motor build. Cometic? Help me please.
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Old 05-09-2009, 07:12 PM   #24
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Quote:
Originally Posted by m0nkeyballz View Post
Sorry to hijack but since were on the discussion of headgaskets to use with different block/heads. I am doing an ej25d block with ej18 heads from my 93 L. I was told that it will be a bolt on affair also. But I am curious as to what headgaskets to use? I think ej257 gaskets would be best. But I also want to raise the compression as this will be an all motor build. Cometic? Help me please.
How dare you hijack my hijacked thread, lol! I don't know the answer sorry but for something as different as that I would almost start your own thread at least for the reason that it would be easier for people to find if searching for that in the future, IMO.
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Old 05-09-2009, 08:32 PM   #25
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Very true man, thanks. Good luck with your build.
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