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Old 08-20-2007, 11:52 PM   #1
AWDWRXLOVER
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Member#: 50267
Join Date: Dec 2003
Chapter/Region: SWIC
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02 built hybrid
sr55/meth/sick speed

Default hybrid w/ 06 wrx short block

i searched and cant find anyone who has done one? Im looking to do a budget hybrid and have a great hookup on this block. Is it worth doing or hold out for sti block?? I have a vf39 setup now and want more tq.
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Old 08-21-2007, 09:21 AM   #2
JMK508
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Its like a STI.....
but it doesn't break

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Someone correct me if i am wrong but i believe that the Shortblocks are the same. So sure go for the budget build
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Old 08-21-2007, 11:45 AM   #3
Kenji815
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Join Date: Jul 2004
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Location: Walnut,CA
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2005 Impreza WRX CGM
95 Black Miata

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wrx shortblock is EJ255
Sti shortblock is EJ257
I believe they are different
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Old 08-21-2007, 01:06 PM   #4
AWDWRXLOVER
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02 built hybrid
sr55/meth/sick speed

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they are different but its hard to nail down what the exact differences are being that there are so many opinions on here.
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Old 08-21-2007, 01:24 PM   #5
LeoNYC
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i've heard that they're exactly the same except for the part #
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Old 08-21-2007, 02:44 PM   #6
Acostafan
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2002 Now with 100%
RDA of 2.5l Goodness!!!

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Sti block has hypercast pistons and rods. Not sure about the EJ255.
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Old 09-03-2007, 10:02 AM   #7
bearpaws1973
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Location: Racine/Kenosha Wi
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1992 Typhoon
06 wrx built to the hilt!

Default Differences

During my research, in buying an ej255 or ej257 what I found is the piston P/N is different, probably accounting for the CR difference, but casting #'s for the block are the same (rod and crank are same part #, I recieved this info from a suby engine builder, name withheld, but he is a quality builder that make some top end motors, and many guys run his built motors). Also during my research I found that 2004-6 sti, forester xt, 2006-7 wrx heads all use the same casting part number, differences have to do with valves and cams, and machining work (ie. the air pump for 2007 sti, 06-07 wrx), after casting though the machine work may be different and the WRX head may have more stock machined from the cylinder head deck, also accounting for a higher CR. I need a sti head to take the measurements to compare. I can this evening however take a measure of the ej255 piston, and ej257 piston and tell you exact measurement differences, if it helps.

Note: This is not the bible, just what I've come up with during my blow up/re-build experience, I did work in a die-cast machine shop auto parts and cast # can be different yet it is the same part.

I can tell you, I have my ej255 open and ej257 right next to each other, that the crank is better machined (on the ej257) but as a machinist myself I can tell you that it would depend on the forging I received, and then the machine work (amount of stock) that was needed to be done (and let's not forget tooling, if I just changed insets in my fly cutter etc. etc.).

You can definately roll with the EJ255 for the build, but look out for CR with stock heads, perhaps an investment in a thicker head gasket is in order. I plan on doing a similar build that you are, with my blown block (255) and I have a set of 2002 wrx heads, after I finish my ej257 block build. If your worried about it I have EJ257 pistons (brand new) you can put in. If not if you run with the stock ej255 pistons and stock head gasket, just make sure your tuning is good.

Last edited by bearpaws1973; 09-03-2007 at 10:15 AM.
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Old 09-06-2007, 09:55 PM   #8
bearpaws1973
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06 wrx built to the hilt!

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Sorry it took me so long, but piston difference, I see so far:

WRX Piston:

Crown to bottom of skirt 51.6mm
dish depth ~4.75mm
Valve relief depth ~5.25 mm

STI Piston
Crown to skirt 51.3 mm
dish depth ~4.68 mm
Valve relief ~5.05 mm

I hope this helps, I'm looking for a set of STI heads and I can give you differences between the 3 (2002-5 wrx, 2006-7 wrx, 2004-7 sti)
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Old 09-23-2007, 04:09 PM   #9
1GR8WRX
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Default Useful

This is really useful information regarding the differences between the EJ255 and EJ257. Can anyone confirm that the pistons are different, beyond the dimensions listed above?

-1GR8WRX
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