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My end goal for my wrx is to get to 350whp. I don’t think that is too unrealistic. E85 is also the end goal to actually make that power. So a pretty nice size fuel system for e85 and I have a VF39 with supporting mods. I have the stock ej205 and I would like to upgrade so I can pass the 300hp mark reliably. Should I build an ej205 or throw a 207 short block in and recondition the stock heads? I’ve heard good and bad things about both. Any unbiased opinions would be much appreciated.
 

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My opinion is to go with the 205. As far as I'm aware you can still source brand new short blocks from Subaru. That's miles better than an unknown situation with the 207 from overseas.

If you are entirely building either the 205 should be easier to source parts and support for although i don't believe there is a large difference between the two.

If i recall correctly there is a jdm ej of some ilk that has a factory closed deck. If I were to source anything from overseas that would be the one I would source personally. I don't know if it makes a difference at your power goals but it would make me feel better.
 

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The 2.1L stroker is easily the best EJ20 build out there.

If you are willing to shell out the money, it's a worthwhile investment for the sake of power. HOWEVER -- the more power and torque you throw at an old GD WRX, the more likely your transmission is going to give up the ghost. Never a guarantee, but it should also never be far from your mind.
 

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If I'm not mistaken. JE makes a hybrid piston you can use that will work with your S20 heads. You could run a 257 shortblock, change the pistons, and bolt on your heads without the need for chamber modifications on the heads.
 

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If I'm not mistaken. JE makes a hybrid piston you can use that will work with your S20 heads. You could run a 257 shortblock, change the pistons, and bolt on your heads without the need for chamber modifications on the heads.
It's not a good idea.

The mismatched head volume creates hotspots and gasflow issues. If you are going to go through the trouble of a rebuild, might as well do it right and machine the heads to support the larger bore of the block.
 

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If I'm not mistaken. JE makes a hybrid piston you can use that will work with your S20 heads. You could run a 257 shortblock, change the pistons, and bolt on your heads without the need for chamber modifications on the heads.
It's not a good idea.

The mismatched head volume creates hotspots and gasflow issues. If you are going to go through the trouble of a rebuild, might as well do it right and machine the heads to support the larger bore of the block.
The reason why I recommended it was because Flatirons tuning posted a video about it. Apparently JE modifies the top of the piston to match the EJ20 combustion chamber. If it’s no good then nvm. Just figured I’d give my .02
 
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