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Old 04-08-2003, 01:04 AM   #1
takumi
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Member#: 6964
Join Date: May 2001
Location: levittown ny us
Vehicle:
2001 impreza
pearl ridge blue

Default crank question

i was wondering if anyone know how strong is a 2.5 rs crank, i want to know how much power can it hold hold up , and how strong is the block, how much can it hold up.

the reason i am asking is b/c i have a 2.5 block and crank , and i want to build it up to a turbo motor. well here hear me out

i wan to take a 2001 rs block and crank
throw on 98 2.5 rs heads (dohc)
rs intake manifold
aftermarket piston,rods, valves, and etc
i plan to sleeve the block and lower the compression

what u think, would it be a bulletproof plan?

if this goes good, i will have rs heads, piston, rods forsale
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Old 04-08-2003, 04:23 AM   #2
rhdude
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Default

get some WRX heads, the MY98 heads flow like crap
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Old 04-08-2003, 08:38 AM   #3
Legacy777
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AWD 6MT EJ22T AWIC Swap

Default

The crank would be the last thing I would worry about.

You're going to kill your rods/pistons/rings/heads long time before you kill your crank.

The amount of main bearings and the smaller size of the crankshaft makes the bottom end very good.
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Old 04-08-2003, 10:27 AM   #4
BOY
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99 RS-T RIP
02 Forster-S

Default

You may want to move this into the AFI forum but Legacy777 is dead on.
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Old 04-08-2003, 11:50 PM   #5
obyone
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The trans would go out long before the crank does.
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Old 04-08-2003, 11:53 PM   #6
Eric SS
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Location: 2013 335i, 2011 G37 coupe
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2000 2.5RS w/ EJ22T
swap and N20. gone. : (

Default

Out of curiosty, why would you want to throw on a set of 98 DOHC heads???
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Old 04-08-2003, 11:54 PM   #7
Eric SS
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2000 2.5RS w/ EJ22T
swap and N20. gone. : (

Default Re: crank question

Quote:
Originally posted by takumi

if this goes good, i will have rs heads, piston, rods forsale
PS: how many A and how many B pistons will you have for sale. I might buy them
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Old 04-09-2003, 11:51 AM   #8
takumi
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Default

cool thanks for the info,
first i thought of using 98 heads is b/c they are dohc unlike mine they are sohc, the other thing i don't understand is why would u use a ej20t heads which goes on a 2.0 litler and put it on a 2.5 litler it just doesn;t makes sence. the reason i thought of that was b/c i heard a wrx used 2.5 litler heads makes it so much better. but then again i am still looking in to this. so keep it coming.


i do plan to use aftermarket pistons and rods, like i stated, i kinda of knew that those are the parts that goes first, thats why i plan to sell them.

and i would not be selling my heads, rods, piston till the end of june or so , if u are interested please e-mail me at griffin604@aol.com so i can e-mail u back when i have them out, unless u can wait that long.

thanks for all the info, please reply with more info. thanks !
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Old 04-09-2003, 12:56 PM   #9
Eric SS
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Location: 2013 335i, 2011 G37 coupe
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2000 2.5RS w/ EJ22T
swap and N20. gone. : (

Default

Quote:
Originally posted by takumi
cool thanks for the info,
first i thought of using 98 heads is b/c they are dohc unlike mine they are sohc,
the SOHC heads flow better than the DOHC heads and they are both 4-valve/cylinder heads. stick with your SOHC heads
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Old 04-09-2003, 07:17 PM   #10
rhdude
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The reason you want to go with the EJ20T heads is because they flow more... the EJ25 heads are built for N/A.. the WRX heads are build for Forced induction... I would almost say wait until you can get some EJ25 STi heads, but they have the variable cam's and you would need the STi ECU and you would only run into problems...
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Old 04-09-2003, 10:04 PM   #11
Eric SS
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Member#: 1914
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Chapter/Region: SWIC
Location: 2013 335i, 2011 G37 coupe
Vehicle:
2000 2.5RS w/ EJ22T
swap and N20. gone. : (

Default

Quote:
Originally posted by rhdude
The reason you want to go with the EJ20T heads is because they flow more... the EJ25 heads are built for N/A.. the WRX heads are build for Forced induction... I would almost say wait until you can get some EJ25 STi heads, but they have the variable cam's and you would need the STi ECU and you would only run into problems...

I honestly don;t have any flow numbers on the SOHC EJ25 heads or the EJ20T heads but I would be willing to bet that with the stock heads and cams, the EJ25's would flow better than the EJ20T heads.

Remember that the EJ25 heads and cams are made to supply enough air to a 2.5L engine that doesn;t have any help from a turbo but the EJ20T heads and cams are only built to supply a 2.0L engine that has help from a turbo, while also keeping it emmissions legal.

There is a reason that an EJ22T transplant with EJ25 SOHC heads and cams make so much more power than an EJ20T motor with the same amount of boost. It's mostly in the heads and cams of the EJ25.
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Old 04-09-2003, 10:15 PM   #12
Eric SS
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Member#: 1914
Join Date: Jul 2000
Chapter/Region: SWIC
Location: 2013 335i, 2011 G37 coupe
Vehicle:
2000 2.5RS w/ EJ22T
swap and N20. gone. : (

Default

BTW, on Cobb's website, he has the stage 1 WRX DOHC cams listed at 208/206@.050 duration and .366 intake and .362 Exhaust.

on the stage 1 SOHC 2.5RS cams, he has it listed as 211@.050 duration and .410" Intake and .350" Exhaust lobe. the STOCK 2.5RS SOHC cams are .375" Intake and .310" exhaust with 232/236 degrees of duration (but this is advertised.

This tells me that the stock 2.5RS SOHC cams are already bigger on the intake than the stock WRX cams. I'm guessing that the stock exhaust duration is larger than the WRX exhaust stock duration which makes up for the lower lift and helps with scavenging. that's probably one main reason that they make so much more power stock for stock.
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