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Old 11-13-2009, 07:15 PM   #26
ozzy370
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Quote:
Originally Posted by Maxwell Power View Post
from my calculations,

8.8:1 with the factory headgasket.
8.5:1 with 0.040" headgasket
Yeah I was getting 8.8:1 with factory HG after resurface. Looks like we are going to run high.
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Old 11-21-2009, 08:46 AM   #27
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Quote:
Originally Posted by Maxwell Power View Post
from my calculations,

8.8:1 with the factory headgasket.
8.5:1 with 0.040" headgasket

Where are you getting the .026" compressed thickness?

Quirt Crawford is telling me the STI HG is .0195" compressed

Thanks

Last edited by BlackJavaPearl04; 11-21-2009 at 01:08 PM. Reason: info update
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Old 11-21-2009, 07:38 PM   #28
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sorry. Typo.
I always get just under .024, and I use 0.024 for my calculations.

does it really matter? .1 isn't a big difference in compression. .3 is a little bit, .5 is a noticeable change, 1 point is a large difference.
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Old 11-21-2009, 07:54 PM   #29
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Great thanks, Ill use .024"
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Old 11-22-2009, 11:32 AM   #30
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i am wondering if the wrx 2.5 is an ej255 is that block and head the same as the 08 legacy ej255 block and head?

i am planning on dropping in cosworth piston rings bearings and head geasket with stock rods/crank. i want to seal the avcs cam and use wrx cam gears with the cosworth cam position sensor bracket.

i guess i won't have a problem with that set up but i was wondering if i could use a crower cam set instead of the plugged avcs cam and how it would perform with a gt 30r.

http://forums.nasioc.com/forums/show....php?t=1831368

62583-4

http://crower.com/misc/m_cat.shtml

any input is welcome. i am planning on running my 02 wrx intake/ecu on this car. i'll be upgrading to Vi-Pek ecu and ppgs shortly after.

thanks gentleman
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Old 11-22-2009, 02:01 PM   #31
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Originally Posted by maxpowr View Post
i am wondering if the wrx 2.5 is an ej255 is that block and head the same as the 08 legacy ej255 block and head?

i am planning on dropping in cosworth piston rings bearings and head geasket with stock rods/crank. i want to seal the avcs cam and use wrx cam gears with the cosworth cam position sensor bracket.

i guess i won't have a problem with that set up but i was wondering if i could use a crower cam set instead of the plugged avcs cam and how it would perform with a gt 30r.

http://forums.nasioc.com/forums/show....php?t=1831368

62583-4

http://crower.com/misc/m_cat.shtml

any input is welcome. i am planning on running my 02 wrx intake/ecu on this car. i'll be upgrading to Vi-Pek ecu and ppgs shortly after.

thanks gentleman
jake
yes, you can run a wrx cam in the head. You just have to be sure to keep the avcs solenoid to provide lubrication to the forward cam journal. Your centerlines might be off a bit. You have to check each cam spec to see if it'll be optimal for your stroke/displacement.
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Old 11-22-2009, 02:21 PM   #32
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i have been reading alot of your threads max and appreciate you spending the time to share with the forum.

i listed the specs for the cam i am considering purchasing. will that cam work without mill work in my ej255 head? what can i expect from them? the spec for the ej205 stage 4 and the ej257 stage 4 appear to be the same. i don't see how they are different. i understand how they would work different under different displacement.

is the 2.5l wrx motor/heads (ej255? really?) and the legacy ej255 motor/heads the same or is the ej255 legacy the same motor/heads as the ej257 motor/heads with different internals?

thanks brother.
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Old 11-22-2009, 02:44 PM   #33
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Adding this one to the archives. Good write up guys!
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Old 11-22-2009, 02:48 PM   #34
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Originally Posted by maxpowr View Post
i have been reading alot of your threads max and appreciate you spending the time to share with the forum.

i listed the specs for the cam i am considering purchasing. will that cam work without mill work in my ej255 head? what can i expect from them? the spec for the ej205 stage 4 and the ej257 stage 4 appear to be the same. i don't see how they are different. i understand how they would work different under different displacement.

is the 2.5l wrx motor/heads (ej255? really?) and the legacy ej255 motor/heads the same or is the ej255 legacy the same motor/heads as the ej257 motor/heads with different internals?

thanks brother.
The legacy ej255 changed based on the year. In 05 it is the same as the STi with the B25 heads. At some point it changed to the D25 heads. I honestly don't know when that break point occurs. Sponaugle is the best one to answer that question. He has tons of spread sheets with all the part numbers/years/applicability.

Jeff, where are you?!? help!

In regards to cams: some cam manufacturers don't spend a whole lot of time developing their grinds. This is shown by the price. You get what you pay for with cams. BC and Crower cams are cheaper for a reason. If both the specs are the same for the 2L and the 2.5L, then that should tell you a little bit about their R&D. My guess is that they just said "screw it, the 2.5 has AVCS" and rely on the tuner to get the right centerlines on the intake. However, the exhaust side should really be different. If it isn't, I'd go with another cam.


-Dominic
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Old 11-22-2009, 03:31 PM   #35
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thank you for your attention sir.

any idea what the cam spec is on an 08 legacy ej255 cam? any idea what head is on the 08 legacy ej255? sounds like a d25. i guess if its marked i can check tomorrow.

so you think the 06 up wrx and the 06 up legacy has the same block/heads/internals?
that would be interesting.

cheers nasioc...bottoms up.
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Old 11-22-2009, 07:51 PM   #36
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thank you for your attention sir.

any idea what the cam spec is on an 08 legacy ej255 cam? any idea what head is on the 08 legacy ej255? sounds like a d25. i guess if its marked i can check tomorrow.

so you think the 06 up wrx and the 06 up legacy has the same block/heads/internals?
that would be interesting.

cheers nasioc...bottoms up.

I don't know the 08 specs. However, the ej255 and ej257 cams are the exact same profile up to 07 at least. I have a thread on the ej255/257 cams too that Jeff chimes in on with a spreadsheet of part numbers there too.
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Old 11-23-2009, 09:02 AM   #37
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if you were to put an EJ255 and an EJ257 head side by side, and say you were to put 272 cams in both heads, would the heads perform differently even though they have the same cams??
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Old 11-23-2009, 09:11 AM   #38
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and hey jake off the record..you wana trade those headers?? haha... u hear me go by this morning? and also another q.. if i were to run a 2.5 block with 2.0 heads, i see it is more knock prone, but couldnt a quality set of cams and a proper tune help prevent this problem??
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Old 11-23-2009, 03:36 PM   #39
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Originally Posted by SikSilvrSuby View Post
if you were to put an EJ255 and an EJ257 head side by side, and say you were to put 272 cams in both heads, would the heads perform differently even though they have the same cams??

again, there is no such thing as an ej255 head. The ej255 came with the B25 and D25 heads based on applicability.

If you were to compare the D25 and B25 head with the same cam, they WOULD perform differently due to the different combustion chamber design and exhaust ports.
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Old 11-25-2009, 11:18 PM   #40
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i'll let you guys know what heads i ended up with.
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Old 02-15-2010, 09:11 AM   #41
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Quote:
Originally Posted by Maxwell Power View Post
I don't know the 08 specs. However, the ej255 and ej257 cams are the exact same profile up to 07 at least. I have a thread on the ej255/257 cams too that Jeff chimes in on with a spreadsheet of part numbers there too.

found the spreadsheets

Quote:
Originally Posted by sponaugle View Post


** NOTE typo I need to fix for the 06 WRX as the block code is 630 not 330. **

Jeff Sponaugle

Followed up by:

Update:

Here is the information on the Legacy:






Last edited by 012.5RS; 02-15-2010 at 10:57 AM.
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Old 07-06-2010, 11:44 PM   #42
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Quote:
Originally Posted by Squidz View Post
Wouldn't the 8.87:1 compression ratio (given an 03 wrx with STI block) be better for low-end torque compared to the stock 8.42:1? I'm looking to get as much power down low as possible out of my build, which is why i was considering the STI over the 2.5 WRX block.

0.45 difference in CR doesn't seem like a lot, but i could see how it might cause a little bit of a funky powerband on a car without variable timing...
Quote:
Originally Posted by 305mouse View Post
You don't want too high of a CR in a forced induction motor. Look at how low the STI's CR is. Part of that is because of the turbo they matched it up with. I will be doing a hybrid motor but am just in the researching phase right now. I personally am looking to keep the CR around 8.4-8.6 just for engine life. Of course you can run a higher CR but then you should run lower boost, unless you just sleeve the block and build the piss out of it and have more money to play with when it comes time to rebuild it.
The only time you should really be conocerned with a high compression is if your going to be running 350+whp.
@ that point youd want to swap out your pistons for some CP pistons or another brand of low compression pistons anyway.
the stock ej257 pistons become questoinable near 400hp ~350whp
0.02
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Old 07-14-2010, 01:27 AM   #43
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A very timely and interesting thread. I find the head differences more intriguing than the piston differences.

Just picked up a 2010 Forester XT motor w/ only 75 miles, after which it developed a knock...going to take it apart, check it out, do a mild hotrod job and put it in the Impreza.

I was offered some inexpensive new STi pistons, but reading above, seems to me that the advantage is negligible, if even existent. Probably better going w/ custom JEs, CPs, or even keeping the stock units in place?

Stock XT is 8.4:1 compared to the STi's marginally lower 8.2:1...do i just keep the stockers and run with a Polka Pickle? Only looking for 300WHP/TQ - knowing the STi pistons aren't (much) different and given I don't think the boost levels to get to 300 warrants forged units...thoughts? Seems the above poster would say "stick with what you got".
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Old 07-14-2010, 06:06 AM   #44
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Was reading, i was wanting to pick up a 257 to do a engine build to run a bigger turbo safer. now im thinking i might be able to use my 255 to build up to run a 18g, only real goal is 300whp. Should i do just pistons and rods on a 8.5:1?
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Old 07-14-2010, 07:15 PM   #45
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if you were to put the ej257 block with d25 heads what head gasket would you want using 93 octane on a vf39?
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Old 04-06-2011, 07:54 AM   #46
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This thead has nice info, is there anywhere I could find head volume for the older jdm engines, specifically ej20k? Thanks
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Old 04-06-2011, 10:23 AM   #47
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Great documentation!
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Old 04-06-2011, 10:57 AM   #48
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Quote:
Originally Posted by 2slofouru
This thead has nice info, is there anywhere I could find head volume for the older jdm engines, specifically ej20k? Thanks
Take a picture. They're either 46.6 or 49.5.
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Old 04-06-2011, 08:20 PM   #49
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I'll post a pic, just a second...

when I got the engine



cleaned,
I cleaned them more after the shave and these pics




original k pistons in car now


Last edited by 2slofouru; 04-06-2011 at 08:28 PM.
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Old 04-06-2011, 08:26 PM   #50
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The cp's are 8.2:1 but non offset pins, wiseco are 8.5:1 and offset oem style, sucky thing is the machine shop who shaved the heads said he only took a tiny amount off but it looked a bit much. Car is still running strong though. Maybe it bumped my compression, would explain the pep.
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