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Old 10-21-2000, 01:22 AM   #1
Scooby Specialist
Member#: 730
Join Date: Jan 2000
Question Recommendations for a turbo prepped EJ25 block?

As you might have guessed from my post on the classifieds, I am cutting the BS and getting the ball rolling.
What would constitute a turbo prepped shortblock?
I know that forged pistons and forged con rods are a necessity, but what about the crankshaft? Is the stocker forged, and will it hold up to a high boost street engine?

What about rings? Gapless? How much would a pre-prepped block run? Would the cost differential of kit vs pre assembled be great enough to warrant me putting the pieces together? I do have experience pulling engines apart and putting them back together, so I could conceivably do the assembly on my own.

I want to know the score before I commit a large sum of money to engine, internals, turbo, ECU, and so forth. I want to get everything up front so I don't end up dragging it out and blowing the budget because I had to do a half assed job to get it running, and go back and do a portion of the build over again.
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Old 10-21-2000, 01:24 AM   #2
TMR Impreza
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Join Date: Aug 1999
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Location: San Pedro
2011 M3 and 328i
white and black


ISR is building my motor. Ed has some tricks up his sleeve. Should be a nice motor.
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Old 10-21-2000, 02:54 AM   #3
Joel Gat, 1.8L
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Join Date: Jun 1999


Trey Cobb can also prep an engine. He works over the blocks, seals the deck, adds the piston backside oil-squirters, bores and hones the block to 100mm (if you want), has forged pistons, 8.5:1 or whatever custom CR you want, etc.


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Old 10-21-2000, 07:50 AM   #4
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Member#: 2052
Join Date: Aug 2000
Location: Baltimore, MD

TMR, there was a typo in your link http://www.autocaresubaru.com.

Anyway, I checked it out. Are you getting a turbo? Which?
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Old 10-21-2000, 10:25 AM   #5
Tim Prudence
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Join Date: Aug 1999
Location: san diego, ca USA

What is your target horsepower/torque?
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Old 10-21-2000, 10:46 AM   #6
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Tim, my target is in the 350-400 range, possibly 450. I've seen that it can be done reliably (by that I mean 100K mile reliably) if you select the right components and follow good assembly guidelines.

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Old 10-21-2000, 10:36 PM   #7
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Join Date: Oct 1999
Chapter/Region: W. Canada
Location: St. Albert, AB, Canada
2004 STi
White on Gold


IIRC, the EJ25 crank is a cast piece. Not sure if you can get 100k reliability at those sort of HP levels.

However, that point may be moot since it appears that a lot of people that are going FI on their EJ25's are having tranny problems long before engine reliability problems.

My 2cents
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Old 10-21-2000, 11:51 PM   #8
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I am *well* aware of the stock RS transmissions tendency to grind 2nd gear to mulch under spirited driving with a turbo. I have contacted a company that makes 450HP capable *HELICAL* (i.e. synchromesh capable) gearsets for the Subaru. So, no dog box in my future.
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Old 10-22-2000, 01:10 PM   #9
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Location: Derby, Derbyshire, England


Uprated main bearings

For that power you wont need to brace the block or go closed deck.

I might even go as far as saying the stock crank would be ok.. but will need balancing...relieving...etc..

But definately do the rods and pistons..

As for compression... I would go for 9.5'ish.. but will depend on fuel and final boost..(simply put)


ps - Ready to be corrected..as per usual
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Old 12-19-2000, 01:46 PM   #10
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2002 S4
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What company is that digital_boy? How much are the gears?
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Old 12-19-2000, 02:41 PM   #11
Homicidal Maniac
Member#: 1612
Join Date: Jun 2000
Location: Austin, TX
2008 STI


You might also want to inquire about this sort of thing to www.b-specusa.com .
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Old 12-19-2000, 02:54 PM   #12
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Chapter/Region: South East
Location: Charlotte, NC

Beat me to it Stimpy www.b-specusa.com has a stronger crank and other goodies and www.cobbtuning.com has everything else you need.

Oh yeah please share the knowledge about the transmission.

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Old 12-20-2000, 05:47 AM   #13
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Location: Lansing, MI
1999 Impreza 2.5RS
Rally Blue Pearl


Digital_Boy, I can't recommend you building the shortblock yourself. The rest you can probably do without really hampering engine reliability(though you may want to have someone assemble the heads, too), but unless you consider yourself an expert engine builder let someone else do it. You're talking about a lot of horsepower out of an engine you expect to last for awhile. In this respect, there is no substitute for an extremely profesionally built shortblock.
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