So.....over the years, there's been lots of questions about "can I bore out my 2.2 to a 2.5?" or "why do the 2.5 have more headgasket problems?"

 

To shedd light on those questions and others, I took some pics today of 3 different phase I, EJ blocks.

 

JDM n/a 2.0

 

USDM n/a 2.2

 

USDM n/a 2.5 (dohc)

 

Can you spot the differences?

 

Here's the EJ20 cylinder barrel...see how much thicker it is? More cooling space between outer case, large area between cylinders, and lastly.....no notches in barrels for bolt access.

 

Here is the EJ22. Pretty thick walls, but less space around for cooling. Smaller space between cylinders, and slight notches for access to the case bolts.

 

Finally the 2.5 Thin walls, very little room for cooling around. Narrow space between 2 cylinders, and there are even larger notches in the barrel for bolt access. In addition to all this, this phase 2.5 uses SMALLER rod bearings???? recipe for disaster.

 

Wish I had an EJ18 apart to compare as well. I can only speculate that they are even thicker walls, no notches, with lot's of room for cooling.

Edited April 7, 201213 yr by Gloyale

 

http://www.cgperformance.com/subaru_block.htm

Yeah, i've seen that type of setup. Fixes some of the issues......but not all. the cylinders are still very close to eachother........leaving a very small area of contact.

 

expensive.

 

And still you see that a 2.0 or 2.2 can't be bored to 2.5

no question Subaru was pushing the envelop on those dimensions. Didn't help that banning asbestos might have come along about the same time. I've read that it lead to a few other brands having iffy headgaskets.

 

and we STILL have folks with newer cars and external drips.

From that linked site, the stock block they show is NOT a turbo block like they suggest.

 

Turbo blocks are semi-closed deck, which seems to be adequate for turbo use with nice high boost. The turbo engines have crappy pistons and eat those, but they don't blow headgaskets like the NA ones do, because they're semi-closed deck.

 

That's an interesting comparison. It would be really interesting to have an ej18 lined up there too. Probably bigger and beefier like you suggest. There have been some people who've put turbos on them with some crazy high boost, and they held it.

From that linked site, the stock block they show is NOT a turbo block like they suggest.

 

Turbo blocks are semi-closed deck, which seems to be adequate for turbo use with nice high boost. The turbo engines have crappy pistons and eat those, but they don't blow headgaskets like the NA ones do, because they're semi-closed deck.

 

That's an interesting comparison. It would be really interesting to have an ej18 lined up there too. Probably bigger and beefier like you suggest. There have been some people who've put turbos on them with some crazy high boost, and they held it.

 

 

 

The text IS confusing - but they just label that an EJ25 without any other letters.

 

no connection with them - just something I recalled seeing. Can't help but wonder if temperature cycling something like that aftermarket mod couldn't result in just as much movement as not closing in the deck. I dunno, CNC stuff is pretty good nowadays.

turbo engines also come with better headgaskets. is that true of the entire line of OEM EJ25T's?

People say you can use the STi gaskets on the ej25D because they're a higher quality MLS gasket that's less likely to blow. Esp. for the franken motor.

Turbo blocks are semi-closed deck

 

False. Most EJ20"t" engines are open deck. I don't know all the jdm versions, but 205s for sure. I think 20Gs and Hs.

False. Most EJ20"t" engines are open deck. I don't know all the jdm versions, but 205s for sure. I think 20Gs and Hs.

 

Should have specified, 2.5 blocks.

Can't say for sure on the cylinder walls, but the 25 certainly has the appearance of thinner walls. Cylinders are definitely visibly closer together. But I notice the cylinder walls on each move progressively further outwards towards the outer walls of the case. So this proves that the blocks are certainly NOT the same, and are not just bored out larger for the next larger size piston to fit in.

 

Another thing I notice on the 25 block, is the size of the indents in the outer part of the cylinder walls. Awfully small distance to the edge of the compression rings.

Anyone that's done multiple HG jobs on those blocks notice if/where there is a typical failure point on the gasket? Could it be nearby those indents?

Where it's clearanced for the bolts that hold the block halves?

Another thing I notice on the 25 block, is the size of the indents in the outer part of the cylinder walls. Awfully small distance to the edge of the compression rings.

Anyone that's done multiple HG jobs on those blocks notice if/where there is a typical failure point on the gasket? Could it be nearby those indents?

 

I'm not sure about HG failure, but I've seen pics of at least one 2.5 block that cracked off a piece of the cylinder,one on each bore, starting from those notches.