Does the EJ25 SOHC and the EJ25 DOHC share the same block?

[subawhatsubawho]

Do they?

I need a fact based answer. Please no guessing.

[BAC5.2]

No.

The Phase 1 EJ25 has the thrust bearing in the center of the crank.

The Phase 2 EJ25 has the thrust bearing at the end of the crank.

Otherwise, construction wise, they should be identical.

It also looks as though you can use a later EJ25 crank (with the thrust bearing surface on the end of the crank), in an earlier block with minor modification.

What, specifically, is your question?

[subawhatsubawho]

fade2black needs a new block for his SOHC 2.5 but I have access to a cheap DOHC 2.5

Can he use my block with his heads?

[BAC5.2]

Yes. No reason he wouldn't be able to.

Compression ratio might bump up. I don't really feel like cramming the numbers right now, but it should still work. The compression ratio would only change because of cylinder head design though.

By the numbers, the Phase 1 and Phase 2 blocks were nearly identical. They moved the thrust bearing, though I'm not exactly sure why. The DOHC has the thrust bearing in the middle, and the SOHC has it at the end of the crank.

Should be good to go.

[555BCTurbo]

They moved the thrust bearing because the motors would develop excessive thrust with time (as mine has )...the relocation supposedly alleviated the problem

[napphappy]

A little more info:
The Phase II block mounts with six bolts and two studs, the phase I is two bolts and two studs. Should still work though.

also
the oil groove in the 1&3 crank journals are modified for better lubercation on hte phase II

[BAC5.2]

None of those things will effect your ability to use that block with your heads though.

[Matt Monson]

Actually,
A couple of corrections to add to this thread. There are really 3 versions of the Ej25 produced between 1996 and 2000.

The first on is the phase I engine that most people talk about. It ran from '96-98. It does have a larger pistion dish than the phase II engines, and would drop his CR using it with the phase II heads. The other difference is the starter mount. Because of the 4 bolt vs 8 bolt design. But for using this block in a later car, it is not an issue because it just has a stud where one of the bolts on the later cars resides.

'99 was a transition year. You will not know if you have a phase I or phase II engine (thrust bearing location) without cracking open the case. Subaru was very inconsistent in when they made the actual switchover. There are phase I '99's with 8 bolts, and phase II '99's with four bolts. It's a real crapshoot. They still used a square top piston, but it had roughly 1 mm less relief than the '96-98 pistons. This was about a 2cc difference and made for a slightly higher CR than before. Again, it would still drop the CR when used with SOHC heads.

Then the full production phase II engines are from '00 on. They have a flat top piston with valve cut outs. This is the only engine that would not alter his CR. As has been mentioned, they are all end thrust and 8 bolt...

[subawhatsubawho]

I'm unsure what year the EJ25 DOHC came out of as it is a JDM engine.