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Old 07-31-2005, 06:18 PM   #1
WebWizard
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Default Swapping Shortblocks

First the Story:::

I put my turbo kit on my car (98 Subaru Impreza 2.5RS), and it was running fine. I decided I wanted to bring it to a dyno to figure out the numbers, and check my fuel/air ratio. Well I figured out my fuel/air ratio. But the guy running the Dyno at the time wasnt paying attention, and put my car past redline and held it there. Running 6 psi and stock internals = fine... Running 6 psi, stock internals, and running past redline = bye bye.... So I know have a knock in my engine. My buddy looked at it and told me that it sounded like a Connecting Rod Bearing broke. So I am not sure how much that is going to cost to fix, but I know its going to hit the bank.... So I decided to start looking around for, re-built shortblocks.

So my question is... Would an STi shortblock bolt up to stock 98 RS heads? And because I have a 4eat would that present a problem? I am not sure if it would, but I wanna get all the info I can before I go forward with buying an STi shortblock... I called dealers in the area, and they told me $1475 for an STi shortblock, and $1900 for a 2.5RS shortblock . So does anyone know if my 4eat is going to be a problem, or if the STi shortblock will bolt right up? I am bringing my car to the dealer tomorrow, and seeing what they say. Worst case is I get a stock 2.5RS shortblock... And I definitely wont take my car to that same Dyno ever again....

Dave
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Old 08-01-2005, 01:35 AM   #2
Master2192
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You will have no problems putting in an STi block. in the FAQ at the top of the page you can find this link on what you need to mate it to your RS heads.

http://forums.nasioc.com/forums/showthread.php?t=601588
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Old 08-01-2005, 08:09 AM   #3
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So the my 98 DOHC heads should bolt right up to the STi shortblock (if I was reading correctly).. All I would need is STi Headgaskets..

But does anyone know if me having a 4eat is going to present any sort of problems, with the STi shortblock?
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Old 08-01-2005, 11:11 AM   #4
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Legos...
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Old 08-01-2005, 11:47 AM   #5
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Not fitment wise but power wise you might want to do some upgrading (TQ and clutchpacks and the like)
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Old 08-01-2005, 12:17 PM   #6
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Depends on how much boost he's planning to push into it
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Old 08-01-2005, 04:51 PM   #7
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Update:

Well, I just talked to the main tech at my dealer. He told me the STi shortblock, shouldnt be a problem, except for my pocket.. He did say that I could run up to 12 psi, if I wanted but my tranny would be dead. I told him I dont plan on running anything past 6 psi for now. But eventually, I wanna run over 12 psi, after I get a new and better tranny that is.

So after finding out that the STi shortblock would fit, he told me he couldnt do it.. He said if he was to do the work, then the car would have to be completely put back to stock (engine, exhaust, everything, etc..). So I am currently looking into local shops, that are willing to put in an STi shortblock for me. I just learned however that I might have a problem when it comes to the headgaskets and cam timing.... << Never planned on that.. So thats another thing I have to look into... Any ideas anyone?

Dave
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Old 08-01-2005, 04:56 PM   #8
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Use the STi headgaskets. As for cam timing, i don't see how it would be any different than your current 2.5L.
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Old 08-01-2005, 08:37 PM   #9
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if you put the ej257 block in there, it will be real slow with 6 psi. dont forget that the compression is way lower. you are going to lose horsepower if you just trade blocks. youll want more boost! your going from like 10.0:1 to about 8.6:1.
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Old 08-01-2005, 09:22 PM   #10
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Boosting a stock 2.5 at 5-6 psi is at least, if not more hp than a 2.0 boosting at 14 psi. This is because of the compression ratio differences. Of course, the 2.0 can keep upping the boost and you can't.

So the same thing goes for the low compression STI block, it needs the 14-15 psi to get the numbers out of it that you would want. I bet 5-6 psi on a STI block would have less power than a stock 2.5.
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Old 08-02-2005, 09:33 AM   #11
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Well my next question is.. How much boost can you put through an STi block with stock 98RS heads, and a 4eat?? I dont think the stock 4eat will be able to handle 14-15 psi... I think after starting my car, I would need a new trans...

I am not worried about some power loss, I just want a block that can handle boost better and will last longer. I dont want to get a stock 2.5 block if I can help it, because then I gotta switch out all the internals. And price wise it will add up to about the same if not more, where if I get an STi short-block all the internals are already strong enough for boost... I plan on running more boost as soon as I can afford a new transmission, or a transmission re-build kit...

So how much boost could I run with the STi shortblock and stock 98RS Heads...safely..

Dave
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Old 08-02-2005, 10:40 AM   #12
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OK. First, the 4EAT can handle more power than the stock 5MT. Just one thing, get a tranny cooler!
Second, you can't just drop in an EJ257 on the car and expect it to run the same. Sure, it'll bolt right up, (just need to modify the water channel that bolts on top of the block), but you need some sort of EM (Engine Management) on there. Since the compression changes, the stock ECU will freak . Now, this has been done on MAF engines, with the help of an SAFC, and it runs decent. But, you're best and safest best is to get EM, period.

-Vic
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Old 08-02-2005, 11:05 AM   #13
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Your dealer tech is talking out his arse, as the points of a few others have made clear. Xephyr runs 25+ psi on an Ej257 w/DOHC EJ25 heads. Another Colorado local runs an Ej22T w/Ej25 heads at a bit fewer psi than that, and puts it through his 4EAT, running 12's at 5000ft. Both the block and the tranny are up to the task before you...

As has been mentioned, you'll want to be running into the teens boost-wise with the lower CR. Get an E-manage or a Perfect Power to aid you in getting the car tuned right. What turbo are you currently running? Is it up to the task of boosting the STi block? Also, you can use a WRX coolant crossover pipe to deal with the water channel issue.

Lastly, where are you? without a location in your signature, it is hard to recommend a local shop to help you out...
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Old 08-02-2005, 03:33 PM   #14
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Well first off, I have to admit I am learning a lot...

Okay, so the STi shortblock will bolt right up. The stock tranny can handle more psi than I think (hopefully around 12-14). A WRX coolant crossover pipe will take care of the water channel issue. And I should run an E-manage because of all the differences in the new block... Okay...

I had originally planned on going with an SAFC2. But I was also checking on Rallitek's website about their perfect power. I understand that the SAFC probably wont do what I would need it to do. So I have been looking at the Perfect Power 6, will this perfect power handle what I need it to?

I plan on using larger injectors (when I can find some that will drop in). I already have my Walboro fuel pump (just need to install it), and I was going to get better fuel rails from outbackmotors.com .... And if the perfect power 6 isnt going to work, then what are some recommendations...

Edit:

Almost forgot... I am running a Garrett T-28 BB.

Last edited by WebWizard; 08-02-2005 at 03:48 PM.
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Old 08-03-2005, 08:35 AM   #15
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I have also heard that I would need custom pistons, because otherwise they would hit the heads no matter what headgasket you used. Does anyone else know if this is true or not? Because I was told by a few people, that all I would need to do is get an STi headgasket....

So i should get the following:

stock STi shortblock
WRX coolant crossover pipe
Perfect Power 6 (from rallitek)
Custom Pistons??? (not sure if needed)

dave
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Old 08-03-2005, 12:25 PM   #16
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Who told you you need pistons? Just get the STi headgasket...
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Old 08-03-2005, 08:30 PM   #17
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It was in a PM I received... Saying that I needed custom pistons otherwise they would hit, and throw off my timing... I am just trying to get all the facts.. And also for the coolant pipe, WRX or STi one would work fine, right? I will look thru my PM's tomorrow and post about needing custom pistons... Thats the first time I heard of that...

dave
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Old 08-03-2005, 09:04 PM   #18
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First PM:
Quote:
The STI shortblock will match to every component in your 98 RS except for the cylinder head / cam timing.
There are two thickness of head gaskets that Subaru uses. The phase one is what is on your car, .059" thick. The phase two is what is on the STI, .0195" thick.
If you put a phase two gasket on a phase one motor, the pistons will hit the heads. And the cam timing will also be off. If you put the phase two gaskets on a phase two block using phase one heads, your cam timing will be off. And if you use the phase one gasket with the phase two block, the squish volume will increase by two hundred percent.

I hope that I have not confused you
Second/Third PM:
Quote:
To propperly use an STI shortblock with your heads, you would need a custom set of pistons and go with the phase one head gaskets.
Every thing else from your car will bolt on the STI block.

On the compression issue, If you choose to go with a set of custom pistons to correct the cam timing issue, I will make them to any compression ratio that you choose
And thats what i was curious about, because no one else said anything about switching pistons off an STi block...

-Dave
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