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Old 07-11-2019, 01:13 PM   #1
Bmarty14
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Default What engine do I have? EJ251, EJ253, EJ255, Ej257??

Basically Iím rebuilding a EJ25 on an 02 Outback Impreza I bought, and I have no idea what pistons to order. I know the bore clearances are super tight for Subaruís and I donít want to get the wrong piston size.ive also read the valve locations are different for each of the EJ25 series engines. Thanks for the help!
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Old 07-11-2019, 02:24 PM   #2
xSacred
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Should say on top of the block just below where the alternator sits and there is another ID from Subaru on the back side crank case near the exhaust ports I believe.
https://www.autopsrus.com/subaru-engine-identification
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Old 07-11-2019, 02:36 PM   #3
ScubaruImpreza05
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EDIT - Fixed, i read a bit more closely. Looks like it is probably an EJ251


Quote:
EJ251

Flat four EJ251
The EJ251SOHC was the first version of a long line of single overhead cam engines by Subaru for the US market. The EJ251 was soon replaced by the EJ253 in many models due to its improved cooling to aid in head gasket life and improved engine management and sensors. The EJ251 commonly experienced head gasket failures resulting in interior channel breaches or exterior fluid leaks due to the continued use of a single layer coated gasket first introduced on the EJ25D. Intake volume is calculated by the use of a MAP sensor, unlike the EJ253 which uses a MAF sensor. Compression ratio is 10:1.

Power ISO: 123 kW (165 hp; 167 PS) @ 5600 RPM and 226 N⋅m (167 lb⋅ft) of torque @ 4400 rpm

Usage:

Impreza 2.5RS, 2.5TS, 2.5OBS 98-03 (US)
Forester 99-04 (US)
Legacy 99-01 (US, 4EAT)
Legacy 99-04 (US)
Outback 00-01 (US, 4EAT)
Outback 02-04 (US)
Baja 03-05 (US)

Last edited by ScubaruImpreza05; 07-11-2019 at 03:09 PM.
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Old 07-11-2019, 03:08 PM   #4
Bmarty14
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Quote:
Originally Posted by ScubaruImpreza05 View Post
Word vomit below. I am not sure if by 'Outback' they meant Legacy outback or Impreza Outback.


Wow, that was a lot of info. Appreciate it man!
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Old 07-11-2019, 03:09 PM   #5
Bmarty14
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I guess that leaves me wondering what bottom end parts are compatible across the board?
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Old 07-11-2019, 03:16 PM   #6
ScubaruImpreza05
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Quote:
Originally Posted by Bmarty14 View Post
I guess that leaves me wondering what bottom end parts are compatible across the board?
From what I have read, the only crankshaft that is different in the EJ25 series engines is the EJ25D, which runs a different size (I want to say 48mm versus a normal 52mm for the other EJ25XXX motors). I don't think the crank journals are different between the EJ25 series motors, but you'd want to at the very least match the rods for stroke size, and pistons would need the right valve on top. My particular EJ253 seems to have more aggressive valve indents on the top. Some EJ pistons look rather flat, so not sure if piston heads are interchangeable or not between motors.

As for the heads....not sure if all EJ25 have the same cooling pathways, jackets, and oil lines or not. I've read (but not confirmed) that alot of the stuff can be swapped with minimal modifications, but that is simply for research and others who have experience to comment on.
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Old 07-12-2019, 11:50 AM   #7
Patrick Olsen
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Quote:
Originally Posted by Bmarty14 View Post
I guess that leaves me wondering what bottom end parts are compatible across the board?
You can go to parts.subaru.com and look at Subaru's own parts listings. When you get to an individual part's page, there's a "What this fits" tab that lists all of the models & years for that part.
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