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Discussion Starter · #1 ·
just wondering what the differences/similarities are between these 2 motors other than the 251 is map and the 253 is maf. I'm talking about internals, heads, block, etc. i'm mostly wondering if the ej253 has the same forged crank as the 251. oh and I'm talking about the ej253 from '99 imprezas/foresters by the way. any insight would really be appreciated, thanks.
 

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Here you can see what is different in the blocks, EJ253 is supported like a EJ205, EJ251 has the end supports like a EJ257 but is missing the thick side supports, basically has no support.

EJ251


EJ253


EJ205 ( Looks really similar to ej253, of course it has better internals though)


Pics from this discussion
http://www.rs25.com/forums/f128/t78398-ej253-vs-ej251.html

The ej253 looks exactly the same as the 251 but with better supports. Are those really thin walls, look the same as the ej257 to me. The ej257 looks to be the same as the ej251 except it has the two extra supports per cylinder top and bottom with small supports like the ej251 on the front and back.

EJ257 ( not sure what year, think they said 06 and i saw an 05 that looks the same)
 

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Discussion Starter · #5 ·

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yep. you heard me.
‘18 E63s AMG wagon & 10 Subarus
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I believe there are negligible differences between the ej251 and the ej253. I think 1 is MAP, 3 is MAF. Other than that, there are very few, insignificant differences.
This. all those pictures above are not accurate, so ignore them.
thanks for the info guys, i have another question thats somewhat related:

i have a 98 impreza with a phase 1 2.2l, would a 98 or a 00-01 jdm ej25D work with my stock harness/ecu? whats the deal with the EGR valve? what else do i have to consider?

I'm thinking about this one:
96 97 98 99 SUBARU LEGACY OUTBACK FORESTER IMPREZA 2.5L DOHC EJ25D ENGINE JDM EJ | eBay

or this one:
JDM EJ25 twincam 2.5L 16-Valve Engine 00 01 Subaru Forester SF9 Legacy Outback | eBay
you should just take a long block (any phase 1 block, doesnt really matter) and swap it out, keeping all your original intake and wiring. no other mods needed, except maybe something weird about the EGR depending on what your engine has currently
 

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I believe there are negligible differences between the ej251 and the ej253. I think 1 is MAP, 3 is MAF. Other than that, there are very few, insignificant differences.
the actual differences in the ej251 and ej253 can be either MAP or MAF depending on the intake manifold that is used. There are slight differences in how the timing of the engine was setup but other than that they are a direct swap in.

My old 99RS engine was a EJ253 (is MAF) i believe, which developed an internal rattle. long story short i found a 2002 impreza ej251 (was MAP) and had it swapped in. I used my existing intake manifold to prevent any changes to the wiring for MAF/MAP. The only thing that needed to be switched from the old engine was the timing components (engine would not start for anything before this). the belt, tensioner and all pullies for the timing belt were swapped. After the changes were made it fired up instantly.
 

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Discussion Starter · #10 ·
i thought the ej253 offered AVCS/AVLS and started being used in 06+ models? or are there 2 EJ253s...
the ej253 was used for the 99MY in some imprezas and foresters, they did not have AVLS. then it was used again in 06+ models with AVLS.

does anyone know how many tranny-engine bolts there are on my car (98)?

still wondering about EGR compatibility on the jdm ej25D and a usdm car?

thanks for all the information guys, its a big help
 

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yep. you heard me.
‘18 E63s AMG wagon & 10 Subarus
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the ej253 was used for the 99MY in some imprezas and foresters, they did not have AVLS. then it was used again in 06+ models with AVLS.

does anyone know how many tranny-engine bolts there are on my car (98)?

still wondering about EGR compatibility on the jdm ej25D and a usdm car?

thanks for all the information guys, its a big help
Ah I didnt know they re-used the EJ253 engine code in the 06+ AVLS engines. I'd seen those heads and engines apart (really interesting IMO) but didnt know that they were also called EJ253. silly subaru.

98, its hard to say. I want to say it will be 4-bolt, and 99+ are 8-bolt, but i could be wrong
 

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Discussion Starter · #12 ·
98, its hard to say. I want to say it will be 4-bolt, and 99+ are 8-bolt, but i could be wrong
i just went out and counted and I'm pretty sure you're right about that. thanks.

also i found this in a different thread but i'm not quite sure what the OP means:

- Take the two electrically operated vacuum valves from the EGR system off the EJ22, and hook them up (electrically, not to any actual vacuum lines) to the new engine. This will stop the check engine light from coming on for the EGR system, since the JDM ej25d doesn't have EGR. Alternatively, I've read you can ground out a pin on the ECU, to trick it into thinking there isn't supposed to be an EGR system

does he mean that i just plug the EGR from my ej22 back into the harness and just leave it as is? i don't understand.
 

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I don't know if he's right, but that is what it looks like he is saying to do. From what I've gathered there is a good chance you could just use your ej22 intake to keep all your electrical/vacuum stuff the same.
 

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Discussion Starter · #15 ·
that makes sense. in theory, i could use ej251 heads on the JDM ej25D with my ej22 intake manifold and the EGR would work? at that point it would definitely be easier just to track down a complete ej251 locally and swap it over.
 

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The early 253 has the stronger cylinder wall supports like in the picture above. The later 253 has the same short block as the 251 with the thinner cyclinder wall supports.
 

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idk the second and third pics (labeled as ej251 and ej205) look like the same block to me. they both have the same cylinder wall thickness and the same gap between the cylinders.
The first picture labeled as ej253 is not what is pictured, but the early ej253 does have similar cylinder support and wall thickness to the ej205 which is what is actually shown based on the pistons that are inside the block.
 

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opendeck251+stiInternals
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Only 99-01 EJ22 intake manifolds (a.k.a Phase II EJ22) fit on EJ251/3 heads, so your 98 intake won't work, neither will the EJ25D manifold.


~Josh~
 
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