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Old 02-21-2006, 06:30 PM   #1
Discjoshie
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Default EJ257 Shortblock in RS

I am thinking about swapping in an EJ257 block and internals into my 2000 2.5RS for boostability (supercharger....). Can I directly swap this in, reusing my stock intake manifold, SOHC heads, accessories, etc. Also, I am going to buy an upgraded clutch and I wanted to be clear what sort I would need; one designed for the RS or does the block require a pull-style clutch as if I were buying an aftermarket clutch for an STi? (maybe a stupid question). Any info you could give me would really help me get started, this could be a very exciting build. Thanks.
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Old 02-21-2006, 06:35 PM   #2
Matt Monson
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Direct bolt on, and the clutch is specific to the tranny, not the block. Legarus...
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Old 02-21-2006, 07:35 PM   #3
west_minist
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What you might need to look at is the final compression with the swapped.
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Old 02-21-2006, 08:14 PM   #4
Discjoshie
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I figured that was the case, Matt. How could I find out the final compression with this block/head combination?
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Old 02-21-2006, 08:15 PM   #5
west_minist
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I guess a final compression test should do it.
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Old 02-21-2006, 08:36 PM   #6
Discjoshie
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I would assume so, thanks. I was wondering if someone already knows the compression from experience with this block so I would know going into the project.
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Old 02-23-2006, 10:16 PM   #7
legacy2003
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i want to say the cr would be 7.8:1.
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Old 02-23-2006, 10:19 PM   #8
west_minist
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Why so low?
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Old 02-24-2006, 11:16 AM   #9
Matt Monson
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I am not sure that it is actually that low. IIRC, EJ205 heads onto an EJ257 block is 8.5 or 8.6:1. The Ej25 heads have a few more cc's than those heads, so I would GUESS around 8.2 or 8.3:1. I could caculate it all out and give you a dead-on number but I am lazy and know a number of guys running the set up, so know that it works, and that's enough for me...
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Old 02-24-2006, 11:52 AM   #10
Master2192
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Ding
http://forums.nasioc.com/forums/showthread.php?t=601588

Quote:
EJ257 with SOHC heads approx 8.4:1
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Old 02-24-2006, 03:24 PM   #11
Matt Monson
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FTW
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Old 02-24-2006, 05:20 PM   #12
Discjoshie
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Nice find. Thanks.
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Old 02-24-2006, 05:28 PM   #13
west_minist
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Out of curiousity, would you have to use the EJ25 gasket or you can change to the STI gasket?

I want to do a swapped in the future with a EJ20 NA head that was on a 10.8:1 compression to the EJ257. To be honest, like how the car feel, sometimes I swear that I am over 11.0:1. JDM makes a simlar engine with 11.5:1, so I do not know if that would be more now but what gasket would I have to use?

Also, would the swapped affect cam timing due to the compression change?
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Old 02-24-2006, 05:38 PM   #14
Master2192
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In the thread I linked it recommended using the STI headgaskets. I think it will change the cam timing but I am not sure in your swap. I know if you use the thinner SOHC gaskets on the 98 DOHC engine it bumps the compression up to approx. 10.5:1. This is how my RS is and I believe it throws off the timing on the left side by 3 degrees, but to verify that I'd have to find the thread again.
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Old 02-24-2006, 09:17 PM   #15
Discjoshie
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How does one correct for the timing change? Does anyone know if there is a change when used with the SOHC RS heads?
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