TheSamba.com :: View topic - Subaru EJ251 vs EJ253 short blocks

Tue Aug 23, 2022 4:04 pm

Subaru EJ251 vs EJ253 short blocks - "Skills"? (This seems like a question for Skills)

Are the 251 and 253 blocks be interchangeable?
I think the answer is yes but the parts counter guy says no (though he's only looking at a screen.)

Interweb says 253 is more recent and 251s had head gasket issues. Per parts counter guy my 1999 has a 253 and my 2004 has a 251 (seems backward.)

What difference are between the 251/253?

I'm thinking of getting a new short block (Reman also avail with oil pump, etc) and wondering why I'd get a 251 if I could get a 253.

Interestingly the 251 is avail and the 253 is not - at least from a VIN search at the dealer.

My two donors
EJ251 2004 Forester JF1SG65634H723620 https://www.vindecoderz.com/EN/check-lookup/JF1SG65634H723620

EJ253 1999 Forester JF1SF6554XH720482
https://www.vindecoderz.com/EN/check-lookup/JF1SF6554XH720482

(Also posting on SubaruVanagon group and will post here the summary of replies from there.)

Wed Aug 24, 2022 9:12 am

I believe there's a difference in compression ratios between the 251 and 253, and I think when I was researching the 253 has the lower compression ratio. Whether a 251 cylinder head would fit on a 253 short block I don't really know.

I'd suggest sticking with the EJ251 short block/cylinder head combo and getting a really good multi-layer steel head gasket kit. I'd also suggest going with the new short block assembly because you'll probably change out the oil pan (shorter), oil pump (higher mm version), and water pump on the Subaru reman anyway.

Wed Aug 24, 2022 10:59 am

same difference really

EJ25 SOHC engines came w/either MAF: EJ253 or MAP: EJ251.

they both use the same heads and head gaskets. one may have the PCV valve that threads into the block, the other into the intake. easy enough to go either way

Sat Sep 10, 2022 8:17 am

I replaced my 251 block with the 253. Everything interchanges fine except the pcv. Easy to deal with using a threaded pipe stub.

Sat Sep 10, 2022 8:57 am

I've read that to solve head gasket issues Subaru replaces them with gasket sets for turbo cars...I have no practical experience with this, just throwing it out there.