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Old 01-21-2021, 09:28 PM   #1
Mindriddle
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Default ej257 short block variations

Noob question. What is the difference between the variance on the short block part numbers? For example, the 10103AC030 vs the 10103AC890?
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Old 01-22-2021, 09:04 AM   #2
Max Capacity
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Old 01-22-2021, 10:37 AM   #3
BlackFighter
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There was a whole thread about those case numbers i can not find it now. Search the forum, should fine it.
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Old 01-22-2021, 12:04 PM   #4
Mindriddle
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Quote:
Originally Posted by BlackFighter View Post
There was a whole thread about those case numbers i can not find it now. Search the forum, should fine it.
I tried looking for it but I guess Im just not using the correct key words.
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Old 01-22-2021, 02:22 PM   #5
Max Capacity
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IMO and from what I learned from Tuners years ago with a 9 second single cam 1.6L Civic at 35PSI, it's all in the tune.

I have a ej257 (April 2012) with over 142,000 trouble free miles with a vf52 on stock fueling dynoed at 21psi. It's all in the tune.

Do you have a Tuner your working with ? That's where you should start, find out what he likes to work with.

Over on the legacygt forum one of the trusted members posted this the other day,

"It is a stock short block, since 2011 Subaru has put the nitrided crank in all of their engines even if the original car did not come with it. I've also heard that all short blocks are built to EJ257 standards, even if the original car was a EJ255.

When you go to buy a short block you have up to 3 choices now, and maybe more...

04-07 Block 10103AC870
08-16 Block 10103AC890
18-20 Block 10103AD020"

Last edited by Max Capacity; 01-22-2021 at 02:28 PM.
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Old 01-22-2021, 06:01 PM   #6
relic48
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Default 10103ac870

The '02-'07 10103AC870 # I recognize from subaru.parts.com as the replacement short block for my '04 forester XT, which I have been told is an ej255
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Old 01-26-2021, 02:05 AM   #7
kharmicresonance
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Cases and rods are all the same.

Subaru only ever acknowledged the blocks as ej25. different castings through the years 701/2/3/4.

The differences in the part numbers you posted were the pistons and crank.

2004-2005 XT/STi/Legacy were the exact same EJ25 with low compression pistons and b25 heads. Later the STi changed to slightly higher compression pistons with the D25 heads. The cranks changed hardening methods.

I still don't know who or what started the ej255 vs ej257 confusion.
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