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Old 09-03-2014, 05:40 PM   #1
hoops06
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Default Ej255 build question

I have a 06 baja ej255 dohc turbo. Can I use any ej255 short block and just put my heads on? First time rebuilding a Subaru. Done ford and Chevys in the past. This motor is new to me. Thanks


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Old 09-03-2014, 11:09 PM   #2
Layvon
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You can use any short block out of a

2004-2015 STi
2006-2014 WRX

2006-201X? FXT / OBXT / LGT just find out when they switched to the new motor for your cut off.. If they have already I don't keep up with those cars too well.

In short, any EJ255/EJ257 will work.

I'd make sure your head surface is clean and not warped. Use a new oil cooler or delete it if the motor blew.
Use a torque plate if rehoning the cyl walls.
Don't use plastigauge
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Old 09-03-2014, 11:59 PM   #3
outfrontmotorsports
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Quote:
Originally Posted by Layvon View Post
You can use any short block out of a

2004-2015 STi2006-2014 WRX

2006-201X? FXT / OBXT / LGT just find out when they switched to the new motor for your cut off.. If they have already I don't keep up with those cars too well.

In short, any EJ255/EJ257 will work.

I'd make sure your head surface is clean and not warped. Use a new oil cooler or delete it if the motor blew.
Use a torque plate if rehoning the cyl walls.
Don't use plastigauge
This is incorrect, the 255 motor has "D" heads, they have a smaller combustion chamber than the W, V and B heads. so it must have 255 pistons or your compression will be raised too much for pump gas. the 255 pistons have about a 2.5cc bigger dish than the pistons from a 257 motor. Yes the blocks are the same but the pistons are not!

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Old 09-04-2014, 06:40 AM   #4
Layvon
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He did not ask if they are the same, He asked if he could use any 255 and the answer is obviously yes. I know the pistons are different compared to the 257 but it would give the OP more options.

Anyone who builds / drops in a motor in a Subaru without at least verifying the tune is pretty foolish.

I politely disagree with the too much compression for pump gas, I've seen some pretty good results from using D25 heads to get the gains of the higher compression / transient response etc.

Last edited by Layvon; 09-04-2014 at 06:49 AM.
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Old 09-04-2014, 10:56 AM   #5
outfrontmotorsports
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Quote:
Originally Posted by Layvon View Post
He did not ask if they are the same, He asked if he could use any 255 and the answer is obviously yes. I know the pistons are different compared to the 257 but it would give the OP more options.

Anyone who builds / drops in a motor in a Subaru without at least verifying the tune is pretty foolish.

I politely disagree with the too much compression for pump gas, I've seen some pretty good results from using D25 heads to get the gains of the higher compression / transient response etc.
The knowledge of the OP is low on Subaru as he stated. it would be a sad day to put any shortblock as you stated and then later find out he has 8.7 cr. it appears this will be a stock build as he is only "swapping heads" as stated. my guess was not planning a tune either.

OP what casting heads do you have? D or B?
the cr of a 257 is 8.3
the cr of a 255 is 8.5

however what is not commonly known is that if the D heads are put on a 257 shortblock the compression goes to 8.7!

I will disagree in that you could make HP gains on pump gas at 8.7 when they are already on the ragged edge at 8.5 with factory lowered boost than a 257.

your first post is accurate in that both blocks could work, but as you stated, allows for more options, I just think more clarification of cr's could have been addressed at the same time in your post

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Old 09-04-2014, 11:06 AM   #6
hoops06
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Thanks. How about the coolant port placement? Is that something I need to look into. I was told not all EJ 255's are in the same place.


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Old 09-04-2014, 11:13 AM   #7
outfrontmotorsports
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Quote:
Originally Posted by hoops06 View Post
Thanks. How about the coolant port placement? Is that something I need to look into. I was told not all EJ 255's are in the same place.


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are you asking about the coolant crossover on the top of your engine? just reuse the one from the original car.

what head castings do you have?
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Old 09-04-2014, 12:41 PM   #8
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Not sure on the heads. I will look into it when I get home. Unfortunately Iam not as knowledged on the tect specs as you. I wish I was. You know your motors. Iam just a backyard mechanic with some background experience of fixing cars and rebuilding motors in the past.
The reason I started this post was because a remanufactured motor is $4800 without the turbo. The guy at the auto parts store suggested I ask this forum on what EJ 225 motor I can just put my heads on. Didn't realize Subaru had four different heads for the same block. Hopefully this won't be to much of a pain in the ass and I can get my Baja back on the road


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Old 09-04-2014, 12:49 PM   #9
BB2006LGT
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Legacy gt guys swap the ej257 block into the ej255 heads all the time with no issues. They do always get it tuned though. That being said, out front is a pretty legit shop and am sure they know what they are talking about. I personally just rebuilt my engine rather than swap short blocks.
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Old 09-04-2014, 05:18 PM   #10
2Fast4U1DAY
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Thats because a few of the years lgt was the same 257 in the sti just different heads IIRC
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Old 09-04-2014, 05:41 PM   #11
hoops06
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So if I go with the EJ 257 I'll have to get it tuned because of the different compression right ? What year LGT should I be searching for?


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Old 09-04-2014, 05:43 PM   #12
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How do I know what heads I have on my motor now D or B?


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Old 09-04-2014, 07:47 PM   #13
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I checked my heads and I have b25's.


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Old 09-05-2014, 11:08 AM   #14
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Quote:
Originally Posted by hoops06 View Post
I checked my heads and I have b25's.


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So then you want to only find/use a 257 block, if you were to use a block fitted with 255 pistons with those heads you would have netted only 8.1 cr



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Old 09-05-2014, 11:53 AM   #15
hoops06
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Thanks. I will be taking the heads off this weekend. Hopefully there in good shape. Since the start of this post I have definitely become more familiar with Subaru engines. Which is good because my son has a O2 Legacy GT and my wife as an 06 Tribeca. I guess you can say were a subi family.



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