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Old 10-23-2008, 03:22 PM   #1
EcksJay
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Default EJ257 internals in an EJ251...

Yes, I know various aspects of this have been discussed many times. However, I have some specific questions that I am looking for answers to..


So, STI pistons and rods will fit in a Phase2 EJ25 with no issues?

What do I do about bearings? STI or EJ251?

Is is a "okay" solution, in that there are better options for what one is doing with the block?

If one is to spend money on STI internals, are there better aftermarket products in the same or close price range?


How does everything fit together? Are the clearances in the piston face sufficient for the valves, or is it too much? Is the CR too low for good street use?

So, one would need: Pistons, rings, con-rods, main bearings. What about wrist pins, STI oil pump and water pump? This of course would be for a turbo build (somewhat pointless to mention, since I'd be looking for a lower CR)

What about cams? When I did my 1.8-2.5 swap on my '93L, I installed some delta cam regrinds, and they really woke the car up. Is there anything out there in a REASONABLE price range for the EJ25 turbo applications?

Intercooler. I have an '02 WRX intercooler in my basement. Would this be too small for this build?

What about turbo? I know there are a million different opinions on this, but I don't want something that hits full boost only in the upper rpm's. What would be a good streetable turbo?

Obviously, I'd be going with a piggyback (emanage or similar). Oh, did I mentin, all this will be going in my '97 OBS....

And last but not least, what about the heads? What improvements, if any, should be made to the heads? Valves, valvesprings, retainers?

I think the most attractive thing about this build (and I could be way wrong) is the relative low cost and ease in comparison to a full on STI swap (wiring and everything)
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Old 10-28-2008, 07:44 AM   #2
nojokesniper
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chack out rs25 there is a member named skully who did this exact build, my question is where does everyone tap in for the oil supply/return lines of the turbo
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Old 10-28-2008, 09:40 AM   #3
Matt Monson
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Skully is a member here as well. On his car specifically he's using Ej25D DOHC NA heads. The beauty of those heads is that they are based off of Ej20K castings and already have the plumbing built into them for the oil and coolant. It's just a matter of removing a couple of plugs and tapping one bung.

On other heads, like SOHC Ej25 or Ej22 heads it's easiest to supply oil from the top of the block and return it to the oil pan. The coolant is often just T-d off of the heater core lines in and out.

Ecksjay,
This is really only a good option is you can get the STi internals for next to nothing AND you have access to a really good tune. It's known that those STi pistons are brittle and don't like detonation or preignition at all and will crack. If you don't have a really good tuning option you might want to consider one of the aftermarket forged piston options that were designed for the STi.

You use the STi rods primarily because the wrist pin location has been moved on the STi pistons. Those rods match the rod bearing journal size on the NA phase II crank, so there's no issue there. Use Cosworth bearings. They cost about half of what factory bearings cost. You can get them from Flatirons Tuning online or any number of other vendors. I just mention Flatirons because I know they have them in stock and they supply me, so I like to plug them.
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Old 10-28-2008, 12:00 PM   #4
nojokesniper
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i have an ej25D and plan to use my stock heads and drop in STI internals but do i need the STI crank or can i use my stock one?
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Old 10-29-2008, 01:45 AM   #5
poormansporsche
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I'm thinking you want to use your stock EJ25D crank because the main bearingss are placed differently in the EJ257.

cheers

poorman
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Old 10-29-2008, 02:19 AM   #6
VIsubi
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forged pistons on a EJ253 for boost or nitrous...who sells the pistons.
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Old 10-30-2008, 01:43 AM   #7
silentt
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Brydon has a thread about this on here. Search for it.
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Old 10-30-2008, 08:31 AM   #8
Matt Monson
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Quote:
Originally Posted by poormansporsche View Post
I'm thinking you want to use your stock EJ25D crank because the main bearingss are placed differently in the EJ257.

cheers

poorman
The Ej25D crank has the wrong journal sizes. You need to use a phase II crank. It doesn't have to be an Ej257 crank, but it has to be a phase II one.
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Old 10-30-2008, 09:00 AM   #9
nojokesniper
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thank you thats what i thought
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Old 10-30-2008, 12:59 PM   #10
poormansporsche
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Is the EJ25D a Phase II engine? I don't remember now.

cheers

poorman


Quote:
Originally Posted by Matt Monson View Post
The Ej25D crank has the wrong journal sizes. You need to use a phase II crank. It doesn't have to be an Ej257 crank, but it has to be a phase II one.
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Old 10-30-2008, 05:07 PM   #11
nojokesniper
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the ej25d is a phase I motor
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Old 10-30-2008, 09:24 PM   #12
ballitch
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EJ25D is phase I.

Not only are the rod bearings 48mm instead of the Phase II's 52mm, but the thrust bearing is on the #3 bearing for Phase I, and located on bearing #5 on the Phase II's.


~Josh~
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Old 10-31-2008, 05:33 AM   #13
EcksJay
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Matt,

thanks for chiming in on my potential build. Looking around, I can get used pistons and rods for less than $300 or so. I know forged pistons are going to run more than that. Any preference?
Oh, there are so many questions.....
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Old 10-31-2008, 08:08 PM   #14
poormansporsche
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That was my impression as well. So using a phase II crank in a phase I block is a problem... no?

cheers

poorman


Quote:
Originally Posted by ballitch View Post
EJ25D is phase I.

Not only are the rod bearings 48mm instead of the Phase II's 52mm, but the thrust bearing is on the #3 bearing for Phase I, and located on bearing #5 on the Phase II's.


~Josh~
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Old 04-18-2009, 10:07 PM   #15
putz
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bump, I would like to know this as well.
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Old 04-19-2009, 03:47 PM   #16
master c
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i used mahle forged pistons from extremepsi.com (look under 02-07 wrx/sti) in the stock bore, work great!!
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Old 04-19-2009, 06:36 PM   #17
nojokesniper
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phase II crank is fine in phase I motor as long as u use rods with the same journal/bearing size
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Old 04-19-2009, 09:43 PM   #18
Matt Monson
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Quote:
Originally Posted by nojokesniper View Post
phase II crank is fine in phase I motor as long as u use rods with the same journal/bearing size
That's correct. My remarks above can be a little confusing but what I was saying there was that if you are using the Ej257 STi rods, you've got to use a phase II crank because of the rod journal size. Like you said, you can mix generations of cranks and blocks as long as you are sure to match the rods to the crank and get the right bearings.
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Old 05-02-2009, 03:52 PM   #19
subienewb29
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Bump im doing the same build.
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