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Old 06-11-2024, 11:29 AM   #1
Raymondt
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Member#: 538253
Join Date: Jun 2024
Location: Virginia
Vehicle:
2001 Forester
Gold

Default ej251-ej255 build? can it be done pros cons.

hello all, so i am new to forums and researching questions that i have. I normally just figure stuff out through service books and logs but it seems that subi motors are time bombs and i want to make sure mine is not set for tomorrow.
So as the story goes i have had a 01 forester for about 10 years now, 5mt lowered nothing really done. i installed a old stillen fpr one year mine went out just for looks, ram air intake and full custom catback. ej251 stock just hit 200k and started having a bunch of problems needless to say my head gasket is blown now.
Now about a month ago a acquired a 2011 wrx motor 50k miles from a coworker that got it switched out from water damage. pretty much it rained really hard and he claimed it was not starting and when it did there was a whining noise from the motor so they replaced it.
now i havent cracked into it yet so i dont actually know whats wrong with it but besides all that, i have a pulled ej251 and what im guessing is a ej255 and im really wanting to know what i can do with them. ive spent the last week searching this forum trying to find somone who has explained there build and havent found exactly what im looking for. so hear is what i have and really wondering where i should go from here.

ej 251 na
sohc
i have a full rebuild kit for it
everything stock that comes with forester

im guessing a ej255t
dohc with it looks like top cam adjusters
turbo and piping

questions:
now there is big debate over sohc and dohc but to keep it simple i want to stay with sohc it looks like a electrical nightmare to switch over. can i just slap the sohc from 251 to the 255 block with turbo gaskets ? what makes short and long block? not looking for horsepower or anything crazy just want to get it turboed and running. what do i need other than subframe to achieve this? i see the stock turbo has coolant and oil lines that the 251 wasn't made for how could i tie what i have with what i want? biggest question should i stay with one or the other and make adjustments? i know the 253 and 257 are more sought after but im working with what i have.
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Last edited by Raymondt; 06-11-2024 at 12:47 PM.
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Old 06-11-2024, 12:30 PM   #2
Raymondt
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Member#: 538253
Join Date: Jun 2024
Location: Virginia
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2001 Forester
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Default

So I just looked at the back of the head and can see clearly d25 on the 255 and l25 on the 251 if this helps on the decision prosses
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Old 06-12-2024, 06:48 PM   #3
THUGnastyRACING
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likely a ton of stuff is incompatible, buy a used ej205 and build a 2.5 bottom end with 2.0 heads aka the ej25 hybrid. I enjoy mine thoroughly.
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Old 06-13-2024, 03:02 PM   #4
cboggess
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87 Yugo
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Short block = case with crank, rods and pistons in it.
Long block = short block + heads, cams and valve lash set

Technically yes you can slap your heads from the EJ251 onto the EJ255 and put it in the car and run it. BUT!!! And this is a pretty big but your compression ratio will be entirely wrong, and it will not run well at all.
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Old 06-13-2024, 03:16 PM   #5
Jedi03
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Location: New Mexico
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you can also swap the pistons around to make the compression ratio you want...iirc the blocks are the same physical size and i know the bore is the same
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