EJ25x block differences?

[jonathan909]

I asked this question in the recent frankenmotor thread but didn't get an answer, so I'd like to give it another shot.

I get that these are engine (and not block) designations, but I find the discussions around them confusing.  What are the differences (if any) between the various EJ25x blocks?  How can one tell them apart, esp. from the outside?

I'm trying to get a handle on this, and the wikipedia article isn't clear, though it suggests that the differences between some of these designations are in which pistons are used, and don't actually represent differences in the block casting, machining, or markings.  Is there a better reference or FAQ around somewhere that breaks all this down?

Edited February 15, 2019 by jonathan909

[GeneralDisorder]

As far as casting differences - the 25D block (96 to 98, 4 bolt bell-housing) has some differences in the water jackets around the cylinder liners making them more prone to head gasket abrasion. You can easily tell these blocks because they say EJ25 and they only have a 4 bolt bell-housing. 

From 99 up to 2002, you find the block (251/253) will have 8 bolts and a 3/4" block breather nipple in the right rear corner (sitting in the car orientation). From 2003 on the block is essentially the same but the PCV valve is located in the block instead of the manifold so the nipple is threaded. Beyond that I don't believe there are significant changes to the block itself on up till 2012 after which the EJ25 was discontinued except for the STI. 

Then you have the 255/257 turbo block which differs in that it has cylinder wall support bridges at the 12 and 6 positions to reinforce the cylinders. Although this is (IMO) of dubious utility because the real problem is that too much cylinder pressure will crack the liner around the area of least support which is where the cylinder wall support has a relief for the head bolts (at about 10 and 2) (ask me how I know....). I doubt there is significant advantage to the "semi closed deck" and when we really want to put in more than ~26 psi of boost we install Darton sleeves and the closed deck bridges are superfluous at that point because the thicker liner handles the rigidity and pressure requirements of 27+ psi. Even the "closed deck" modifications that some people buy in on are really just a half-baked solution. The real solution is to bore out the liners and install heavy walled sleeves. Then you don't even need to close the deck - which has ramifications in that the ability to flow coolant is reduced. It is cheaper but again like the factory semi-closed arrangement it leaves the thin factory liners, and generally requires boring to the next oversize due to shifting of the bore to deck alignment in the process of installing the deck plating which leaves the liners even thinner..... don't get me started on this nonsense!

GD

Edited February 15, 2019 by GeneralDisorder

[carfreak85]

As the cars get older and become legal to import we may see an increase in the number of EJ20G blocks floating around in the states.  This same block is still being used in all Subaru factory-backed motorsports programs that are allowed to run the 2.0l displacement.  Nurburgring challenge car, ARA cars, Isle of Mann, etc., they all run the EJ20G with the fully closed deck.

[jonathan909]

1 hour ago, GeneralDisorder said:

As far as casting differences - the 25D block (96 to 98, 4 bolt bell-housing) has some differences in the water jackets around the cylinder liners making them more prone to head gasket abrasion. You can easily tell these blocks because they say EJ25 and they only have a 4 bolt bell-housing. 

From 99 up to 2002, you find the block (251/253) will have 8 bolts and a 3/4" block breather nipple in the right rear corner (sitting in the car orientation). From 2003 on the block is essentially the same but the PCV valve is located in the block instead of the manifold so the nipple is threaded.

Then you have the 255/257 turbo block which differs in that it has cylinder wall support bridges at the 12 and 6 positions to reinforce the cylinders. Although this is (IMO) of dubious utility because the real problem is that too much cylinder pressure will crack the liner around the area of least support which is where the block is has a relief for the head bolts. I doubt there is significant advantage to the "semi closed deck" and when we really want to put in more than ~26 psi of boost we install darton sleeves and the closed deck bridges are superfluous at that point because the thicker liner handles the rigidity and pressure requirements of 27+ psi. 

GD

Thanks for that - very helpful.  Not as many blocks as the numeric designations suggest.  If you happen to find the time to post a few pics showing the differences you described, I'm sure many (including me)  would find them useful.

One of the reasons I'm trying to get an understanding of this is that I may have a chance to pick up a 2010 WRX hatchback that the owner blew by doing his own oil change and not tightening the drain plug (no comment).  He said that it has a 255, which fits with what you said.  He didn't specify turbo, so I don't know what's up on that front - do they all have it?

And I have no clue what this thing should be worth in its present state.

[carfreak85]

NASIOC has had lots of this sort of discussion over the years.  If you search for the "EJ207 Owners" thread you will learn a lot about the later JDM 2.0L engines and how they compare to the EJ255/7 blocks.  There is another thread about the Willal (sp?) billet block on NASIOC that I think has some comparisons to the stock EJ block.

[jonathan909]

Is there a reason for me to be interested in the EJ20?  I was just asking about the EJ25x.

[carfreak85]

Well, out of the box the EJ207 is simply a better engine.  It's the base for all of Subaru's high output street cars since 2001.  Revs 1k rpm higher, I read that it is a smoother revving engine too.  V7 EJ207 may have forged pistons from the factory.  The cost of a used EJ207 is equivalent to the parts and labor needed to replace an EJ257.  People who have gone with the EJ207 seem to swear by it.

@GeneralDisorder You guys play with the EJ207 much?

[jonathan909]

Are you telling me that an EJ207 is a drop-in replacement for an EJ255 and has no less power?

[GeneralDisorder]

28 minutes ago, jonathan909 said:

Are you telling me that an EJ207 is a drop-in replacement for an EJ255 and has no less power?

Depends on what you mean by less power. The 2 liter makes power higher in the rpm range. Honestly the EJ25 turbo is a much weaker engine than the 207. And some 207's come stock with forged pistons. There are plenty of 2 liter engines that make a TON more power (somewhat reliably) than any of the EJ's. The 4G63 is easily capable of much more. 500 is a low number for the 4G. 

The 207 revs faster, climbs higher, and will handle more boost stock due to thicker cylinder walls. 

GD

[jonathan909]

Okay, but keep in mind that I'm not a modder or a rodder - my present interest is in what I might use as a replacement in this 2010 WRX.  As such, my firs thinking is "stock", since if I go ahead with it I'm more likely to sell than keep it.  On the other hand, if this is a desirable combo for the performance crowd, perhaps I should consider it.

[edit]

Actually, here's a question:  I may be able to get my hands on a crashed Forester that (according to the shock tower plate) has an EJ20GDX1NY engine.  Might that be a candidate?  If so, how much other stuff needs to be screwed with?

Edited February 15, 2019 by jonathan909

[carfreak85]

On ‎2‎/‎15‎/‎2019 at 1:37 PM, GeneralDisorder said:

There are plenty of 2 liter engines that make a TON more power (somewhat reliably) than any of the EJ's. The 4G63 is easily capable of much more. 500 is a low number for the 4G.

Keep that trash in the street, not in our house!

[GeneralDisorder]

14 hours ago, carfreak85 said:

Keep that trash in the street, not in our house!

I wish I could. I hate working on EVO's. But the owners are crazy and they bring in 50% more labor for virtually any job that isn't spark plugs. English Racing makes an absolute killing off those fools and I've witnessed their "work" first hand. No comment. 

GD