STi Short Block - Subaru WRX Forum
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#1 Old 08-27-2005, 04:30 PM
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STi Short Block

I'm planning on dropping the money into getting an STi short block and matting it onto the EJ20 head. I was wondering if anybody has done this mod yet, if there are any problems, or if this would even work at all. I know I need to get my ecu retuned, but I planned on doing that with the TXS UTEC. Thanks in advance.
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#2 Old 08-27-2005, 05:04 PM
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There was just a write up about this in SubieSport. I know it worked, but the guy also did some head work while it was out like changing the exhaust valves to the sodium filled STi one and I also think he may have dropped a new cam in as well. I'll see if I can find it laying around the house, I forget where I put stuff alot.
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#3 Old 08-30-2005, 09:44 PM
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yes many have done it with great success, the rex heads bolt right up. may want to search nasioc.com for more info, keep in mind the added TQ from the displacement is rough on the wrx tranny, so i would start saving for that next if you plan the 2.5 swap.
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#4 Old 08-30-2005, 10:07 PM
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Isn't calling it a "small block" sorta a given? I mean, how many 4 cyl big blocks are there?

Brandon
02 WRX Cobb Stage 2 now SOLD to my father who sold it to my Brother. Have fun Al!
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#5 Old 08-30-2005, 11:02 PM
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You misread it. It says short block, not small block.
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#6 Old 08-30-2005, 11:58 PM
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ahh... thanks... *herknav kicks himself

So what is the difference between a short block and... ? Isn't a boxer-style engine pretty short to begin with?

Brandon
02 WRX Cobb Stage 2 now SOLD to my father who sold it to my Brother. Have fun Al!
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#7 Old 08-31-2005, 07:46 AM
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I short block only includes the block itself, piston, rods, cranks, etc. The long block includes the cyl. heads, intake manifold, etc. Shortblock = bottom end, Long block = top and bottom end.
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#8 Old 09-01-2005, 11:11 AM
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That is a cool idea, post pics of the build if you can, thatd be interesting.

Gregory-
keep it in the dirt.
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#9 Old 09-01-2005, 01:06 PM
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Definitely do your research on this. You have to change out your pistons as well, from what I remember reading. Something to do with the stockers hitting the valves on the Stock WRX heads. Crawford Pistons I believe makes the repalcement piston of choice for the STi Shortblock, and it's not too expensive. Just make sure you do all the research before diving into this, as you don't want to learn from your mistakes when you can learn from others.

Blue
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#10 Old 09-06-2005, 05:31 PM
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In Responce to "BlueDeamon" comments, you don't need to change out the Pistons that are in the Stock STI Short Block when matting it up to WRX Stock heads.. The only thing is that your compression will go from 8.5 to 8.6 of even 8.7.. Keep this in mind if you are planning on boosting the heck out of you WRX.. Make sure you have the fuel.. Any way, I am currently in the same process of dropping in and STI Block becuase I melted down a Stock WRX piston (still looking for that problem before I drop the money into that new STI Block) Check out my profile and photo gallery for the Picture of the piston...

Ohh, yea, my information came from Darrly at Ultimate-Racing.com. He said they did a "Ton" of STI drop ins for WRXs and they worked out really well..

02 WRX.. "It's fun when it runs.. Problem is that it hardly ever does..."
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#11 Old 09-06-2005, 11:56 PM
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Well, from all the research I did on 2.5 STi block swaps, I found that you have to do a piston swap, to insure that you don't screw up your pistons. Otherwise, you're looking at hitting you valves and not having the proper compression ratio.

Blue
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#12 Old 09-07-2005, 12:17 AM
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check the forums at rallitek.com they told me that any customer that comes in with a bent rod or anything like that they upgrade them to a STI shortblock and they do a lot of those conversions.
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#13 Old 09-12-2005, 09:29 PM
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Sti upgrade

Yea the compression goes up.. but only to 8.6 or 8.7 from 8.5... not that big of a deal unless you are a hugh booster.. The valve clearence however is not an issue..

02 WRX.. "It's fun when it runs.. Problem is that it hardly ever does..."
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#14 Old 09-12-2005, 10:15 PM
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Quote:
Originally Posted by LiL Shoaf
Yea the compression goes up.. but only to 8.6 or 8.7 from 8.5... not that big of a deal unless you are a hugh booster.. The valve clearence however is not an issue..

This is from I-Speed and Crawford Performance:
Quote:
Also, we do not know if people are telling you this, but we have been told be several Subaru Reps and Subaru dealers that the 2.5 STI short block will ONLY work with the 2.5 STi heads. Well, that's not entirely true.
With the help of our engine builder, Crawford Performance, we can now get the new 2.5 STI block to work with USDM WRX heads! We keep the 2.5 STi turbo crank and rods and use special forged Crawford pistons. These Crawford pistons keep the proper compression ratios that the wrx heads need to operate effectively. Without specially designed pistons in place of the STI pistonsÖthe 2.5 STI block will not work with the wrx heads.

Keeping the stock STI pistons with the USDM heads will get you "excessive compression". We also noted that you may have "valve to piston interference".

Excessive compression, per Crawford Performance, would be 10% higher than stock.
If you want to try and see if it'll do any damage, be my guest. Personally, I'd go with the CP pistons.

Blue
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#15 Old 09-14-2005, 03:28 PM
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How much does it cost to do all the work & purchase the short block, pistons etc. Work done at a pro shop. Just need a rough estimate. thanks...
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