2012 Short block Question Ej25 VS Ej20?
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This is a discussion on 2012 Short block Question Ej25 VS Ej20? within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; Hello All, I have a 2012 WRX premium with 95,000 Miles on it. (I drive about 5000 miles a month.) ...

  1. #1
    Registered User cctoast's Avatar
    Join Date
    Sep 2012
    Montpelier, VT

    2012 Short block Question Ej25 VS Ej20?

    Hello All,

    I have a 2012 WRX premium with 95,000 Miles on it. (I drive about 5000 miles a month.) I have been wanting to make more power for some time now. Up until this point, i've mainly been focused on suspension and driveline mods. I'm not really sure where to begin in terms of the motor itself... I'm not going to be the guy to ask "how much HP can a stock motor take." Because honestly, there are to many variables for me to get a comfortable answer. My goal is around 350-375, id never need more than that.

    I would like to build the bottom end, but, due to my current situation, I cannot go without my car for more than a week or two. What I have thought of doing is finding another EJ25 bottom end; I've also thought of finding a semi-closed deck block from an older Ej20. If I was to find an older EJ20 block, could I run a 2.5 crank and 2.5 heads? Is the bore on those two blocks the same? Once I had the block, I could assemble it, pull the old motor, send the heads off to be machined and re-install etc.

    SO I guess my main question is, how much variation is there engine internal wise in the older WRXs and STIs when comparing them to their "newer" counterparts? Are parts relatively interchangeable? Also, does anyone have a "preferred" brand of Rod/Piston? I will be using all OEM Subaru gaskets and seals. Any assistance at all would be greatly appreciated.

    I am an Automotive Technology Student, so I do have some knowledge in the area, but I'm still new to Subarus and am looking for advice from people who are more comfortable with them than I.


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  3. #2
    Registered User lytlec's Avatar
    Join Date
    Jan 2009
    Central PA
    Do you have any engine mods at all? I would bet that a downpipe and a custom tune would make you pretty happy. In my opinion it seems wasteful to spend money on building up a shortblock if it doesn't need it. When my compression was really low I did replace my short block with an STi short block and I put forged pistons in it...and i think I am pretty well off for now with only 330whp.
    <-------- Taylor Swift.
    2006 WRX 330whp. 300wtq. Slow.
    Hawk-Eye Alliance #137
    First Mods...what to do.
    Subaru Guide

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