Jump to content


Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse
 

Photo
- - - - -

99 Ej25D w/ 251 pistons?


  • Please log in to reply
10 replies to this topic

#1 96LegacyEJ22

96LegacyEJ22

    USMB Regular

  • Members
  • PipPipPip
  • 54 posts
  • Portland

Posted 12 December 2013 - 09:55 PM

I have a good 99 EJ25D and a spare set of 251 pistons. Curious if the Rods from the 52mm Ej25D will work with the 251 pistons. Or if the stroke is different?

 

So pretty much 99 EJ25D block, crank, rods w/ Ej251 Pistons. 



#2 ocei77

ocei77

    Eat, Live, Breath Subaru

  • Members
  • 436 posts
  • Monticello,NY

Posted 12 December 2013 - 11:18 PM

The stroke is the same, 79mm, but the actual A and B piston diameters are different. Attached are spec sheets.

 

O.

Attached Files



#3 robm

robm

    Subaru Nut

  • Members
  • 748 posts
  • Terrace, B.C.

Posted 13 December 2013 - 01:03 PM

????

From the specs you gave, the pistons are the same?

 

If 251 pistons don't fit, why not?



#4 ocei77

ocei77

    Eat, Live, Breath Subaru

  • Members
  • 436 posts
  • Monticello,NY

Posted 13 December 2013 - 01:22 PM

Not saying they won't fit, but you have to check the diameter of the ones you have versus your actual bore diameter.

This will insure that you will get the best fit. An A piston in a B bore will leave more room for the piston to wiggle, accentuating the possible of getting piston slap. On the other side, a B piston in an A bore with std rings will lead to undue wear of the rings.

 

O.



#5 86BRATMAN

86BRATMAN

    Subaru Master

  • Members
  • 3,231 posts
  • Tazewell Virginia

Posted 13 December 2013 - 02:30 PM

They'll fit just fine as long as you match a to a and b to b, I've actually done this with a 25d block.

btw, "a" is bigger than "b" you've got it backwards above

Edited by 86BRATMAN, 13 December 2013 - 02:32 PM.


#6 96LegacyEJ22

96LegacyEJ22

    USMB Regular

  • Members
  • PipPipPip
  • 54 posts
  • Portland

Posted 13 December 2013 - 02:40 PM

Were you able to use the 25D rods?



#7 johnceggleston

johnceggleston

    Lite Master of the Subaru

  • Gold Subscribers
  • 6,228 posts
  • Virginia

Posted 13 December 2013 - 05:02 PM

99 EJ25D block, crank, rods ?

 

first, is it in fact a 99 ej25d block? (count the engine to trans bolts)

if yes, then  it is in fact already a phase 2 block, ej251 .

 

the 99 forester was / is a phase 2,  ej251 SOHC engine. (maybe ej253 depending on the trans, but the same block)

the 99 outback and GT were / are a hybrid engine from the factory,

ej251 phase 2 block with ej25d DOHC heads and intake.

 

i'm not sure what the internals are,

except to say the phase 2 blocks must have the phase 2 crank with the thrust bearing in the 5th position.


Edited by johnceggleston, 13 December 2013 - 05:05 PM.


#8 96LegacyEJ22

96LegacyEJ22

    USMB Regular

  • Members
  • PipPipPip
  • 54 posts
  • Portland

Posted 13 December 2013 - 07:37 PM

8 bolt's on the bell housing. 

 

So essentially I can use the 251 pistons to up the compression for my frakenmotor build and run an STI HG on the Phase 2 EJ25D just like I would with a 251?



#9 johnceggleston

johnceggleston

    Lite Master of the Subaru

  • Gold Subscribers
  • 6,228 posts
  • Virginia

Posted 13 December 2013 - 10:16 PM

there is some concern that the 251 block and pistons may interfere with the valves of the ej25d heads.

and it is recommended that a thicker head gasket is used to eliminate that possibility.

and i don't know if this concern is based on experience or speculation.

but i do know you can use an ej251 block, 00 - 04 as a replacement for an ej25D, 96 - 98 block.

 

but if the turbo head gasket is thicker, i would use that just in case.

of course, the thicker gasket may offset any gain in compression from using the 251 block and pistons.

 

what heads are you planning on using?



#10 Fairtax4me

Fairtax4me

    Su bah roo'n

  • Gold Subscribers
  • 8,531 posts
  • Charlottesburg, VA

Posted 13 December 2013 - 10:33 PM

You already have a 251 short block.
Pull the heads and check the pistons. They're probably the same as the spares set you have.

#11 86BRATMAN

86BRATMAN

    Subaru Master

  • Members
  • 3,231 posts
  • Tazewell Virginia

Posted 13 December 2013 - 10:40 PM

Yes we used the 25d rods, it was a 97 shortblock and they went in no problem. No protrusion from the cyl like the 25d normally does.

The 99 25d uses the same pistons as the 97/98, as long as you're sure the pistons are 251 then you are good. Use some STi head gaskets and 25d heads and enjoy high compression.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users