ej257 short block variations

Mindriddle · 01-21-2021, 09:28 PM

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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Max Capacity · 01-22-2021, 09:04 AM

https://www.flatironstuning.com/blog...5-and-an-ej257

You may find the answer there.

BlackFighter · 01-22-2021, 10:37 AM

There was a whole thread about those case numbers i can not find it now. Search the forum, should fine it.

Mindriddle · 01-22-2021, 12:04 PM

Quote:

Originally Posted by BlackFighter

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.

Max Capacity · 01-22-2021, 02:22 PM

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"

relic48 · 01-22-2021, 06:01 PM

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

kharmicresonance · 01-26-2021, 02:05 AM

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.

01-21-2021, 09:28 PM	#1
Mindriddle Scooby Newbie Member#: 491668 Join Date: Sep 2018	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? * Registered users of the site do not see these ads.

01-22-2021, 02:22 PM	#5
Max Capacity Scooby Specialist Member#: 149347 Join Date: May 2007 Chapter/Region: NESIC Location: Tolland, CT Vehicle: 05 LGT,09 SpecB Black/silver	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.

01-22-2021, 06:01 PM	#6
relic48 Scooby Newbie Member#: 408588 Join Date: Dec 2014	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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01-22-2021, 09:04 AM	#2
Max Capacity Scooby Specialist Member#: 149347 Join Date: May 2007 Chapter/Region: NESIC Location: Tolland, CT Vehicle: 05 LGT,09 SpecB Black/silver	https://www.flatironstuning.com/blog...5-and-an-ej257 You may find the answer there.

01-22-2021, 10:37 AM	#3
BlackFighter Scooby Specialist Member#: 193940 Join Date: Nov 2008 Location: Philly Vehicle: 2004 WRX STI Black RalliSpec Shortblock	There was a whole thread about those case numbers i can not find it now. Search the forum, should fine it.

01-26-2021, 02:05 AM	#7
kharmicresonance Scooby Newbie Member#: 461898 Join Date: Jan 2017 Chapter/Region: MWSOC Location: Ohio Vehicle: 2004 Forester XT MT 01G	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.