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Old 10-17-2018, 01:49 PM   #1
Former Vendor
Member#: 490792
Join Date: Aug 2018
Chapter/Region: NWIC
Location: Medical Lake, Washington
2006 Legacy GT

Unhappy Changes in the FB Series Block??

So we are in the process of doing a rebuild on a customers FB25 out of a 2012 Forester. We were under the impression that all FB motors (short blocks) were the same so we built a core that we had laying around out of a 2016 Legacy. Luckily we got the customer's core here before we sent the new motor because when we compared them side-by-side they were different:

1) There are two breather tubes on the top near the bell housing on either block half on the 2011 but not on the 2016
20181017_093812 by Sunwest Automotive, on Flickr

20181017_093838 by Sunwest Automotive, on Flickr

2) When honing the block we noticed also the webbing in the bottom of the cylinder was shallower on the on the 2011 than on the 2016.

I know Subaru had terrible issues with oil consumption for the first few years of the FB blocks and I've read that they supposedly fixed the issue, but how? What did they do? Does anyone know what they changed and when? Are there things that we as engine builders could do to update the earlier style blocks and if not, what do customers have to do to their vehicle to update it to accept the newer style block?

I'm at a loss so any suggestions or help would be greatly appreciated!:confuse d::
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Old 10-17-2018, 10:19 PM   #2
Elbert Bass
Scooby Specialist
Member#: 283429
Join Date: May 2011
Chapter/Region: South East
Location: Down yonder.
2016 Fuji Sunfire 03


Yup, Suby is only telling use the major changes with new models - not the small incremental mid run differences.We are running into the same thing trying to quote used engines for broke customers.
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Old 10-17-2018, 10:47 PM   #3
Scooby Specialist
Member#: 220971
Join Date: Aug 2009
Chapter/Region: South East
Location: West, NC
2002 WRX 223K Mi.


Surface Treatment Change To Oil Control Piston Rings , Revised piston rings, the black baffle on the block under the a/c compressor gets replaced.

Only the 11-13 Foresters have that external PCV crossover , The ones that usually take 5.8ish qts of oil , vs the later ones that are 5.2ish qts

Block Part# Interchange
10103AC650 = 2014-2015MY Forester & 2013-2014MY Legacy & Outback
10103AC760 = 2013MY XV Crosstrek 2.0L CVT & 2013-2015MY XV Crosstrek 2.0L MT
10103AC750 = 2012-2013MY Impreza 2.0L CVT & 2012-2015MY Impreza 2.0L MT
10103AC660 = 2011-2013MY Forester

Everything after these models have the revised rings from the factory.

NOTE! OEM Short blocks are not interchangeable between transmission types. The Reman update part numbers above will Interchange for either transmission in their respective application.

Last edited by Blktrax; 10-17-2018 at 11:20 PM.
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