2.0 block bored out for 2.5 sti pistons.. Any thoughts?? - Subaru WRX Forum
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#1 Old 06-02-2006, 11:18 AM
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2.0 block bored out for 2.5 sti pistons.. Any thoughts??

Ok guys, here is the question of the day.. I am thinking about what to do with all my "OLD" parts.. I was thinking about doing this..

Re-boring my old 2.0L block to a 2.5L and installing my Stock STI Pistons from my short block into it.. It would not be a true 2.5, as the stroke would be shorter.. What do you think it would run like...

Stock 2.0 Stock 2.5 (NA)

Bore 3.62 in 3.92 in

Stroke 2.95 in 3.11 in

That would make it a 3.92 in bore with a 2.95 stroke.. I would keep the stock 2.0 rods as I don't want to spend any money on this.. I have access to a boring machine..

02 WRX.. "It's fun when it runs.. Problem is that it hardly ever does..."
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#2 Old 06-02-2006, 11:50 AM
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sounds like a "boring" job to me ! sorry, no pun intended.
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#3 Old 06-02-2006, 12:36 PM
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Sounds like it would be a more torquey little 2L? That would increase the CR correct?

My car is well, it's like 10 lbs of shit in a 5 lb bag...

<------ Click to see what I'm workin' with. ;)
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#4 Old 06-04-2006, 09:57 AM
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Is there really enough sleeve material in the WRX block to increase the bore that much? I would imagine the open deck block bored out that much would be pretty unstable in regards to cylinder wall strength.

Probably a lot more cost/effort than it is worth, if it's even feasible.

FP Green'd 04 STi

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#5 Old 06-04-2006, 10:03 AM
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T wrex did you even read what he wrote? He already has the parts he can do it for free.

Sounds like a project lil shoaf if you have some free time. What can it hurt?

What are your plans with th motor? sell it or use it in something else?
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#6 Old 06-04-2006, 10:16 AM
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I think Shoaf will probably keep the sucker as a "just in case" motor.

Big Jae -
JDM version 7 bugeye
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#7 Old 06-04-2006, 11:57 AM
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i didnt even know u could bore it out that much. thats gonna be a slim fit. but shit. its a worth a try.

▼SbiΣ Mi▼
mike
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#8 Old 06-04-2006, 12:28 PM
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I'm actually looking to sell this thing.. My next goal is a 2.8L so I don't need the 2.0....

To put things in perspective.. The bore difference is only .030" Diameter.. That is only .015" off the wall thickness.. A 1/16" is .0625.. Most guys will say you can bore out the average car 30 over, i.e. .030" with out danger..

I honestly don't know how this thing would act.. I am however curious as all hell, but I don't really want to do it and sell it just have it blow up or run like crap for someone else.. I'm just not that kinda guy.. I think it's time to call my engine builder...

02 WRX.. "It's fun when it runs.. Problem is that it hardly ever does..."
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#9 Old 06-14-2006, 08:02 AM
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dont forget to measure bore thickness and piston pin center to piston top height and compare the dimensions of the 92mm pistons with the 99mm pistons as you wouldnt wanna do it and find the piston to deck height is out by 1mm...piston to head contact would suck or comp ratio of 5:1 because it sits 2mm lower than the deck would suck too but you could run 42psi all day long
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#10 Old 06-14-2006, 10:09 AM
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Dang, I completely neglected to think about that piston wrist pin location..

02 WRX.. "It's fun when it runs.. Problem is that it hardly ever does..."
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#11 Old 06-14-2006, 10:23 AM
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wow i totally missed this thread. Ken this would be a kick ass idea bro, however i would also worry about how thin you are able to bore those cylinders.

Chris- ▼SbiΣ Mi▼
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#12 Old 06-14-2006, 06:19 PM
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Quote:
Originally Posted by LiL Shoaf
Ok guys, here is the question of the day.. I am thinking about what to do with all my "OLD" parts.. I was thinking about doing this..

Re-boring my old 2.0L block to a 2.5L and installing my Stock STI Pistons from my short block into it.. It would not be a true 2.5, as the stroke would be shorter.. What do you think it would run like...

Stock 2.0 Stock 2.5 (NA)

Bore 3.62 in 3.92 in

Stroke 2.95 in 3.11 in

That would make it a 3.92 in bore with a 2.95 stroke.. I would keep the stock 2.0 rods as I don't want to spend any money on this.. I have access to a boring machine..
I wouldn't bore it to 2.5....2.3 would be good and safe

http://www.bpmsports.com/products/stro.htm


additionally the stock WRX rods are pretty weak and won't hold up with the abuse a 2.5L would dish out....it could be a good experiment..but I think it would also be a bomb

"Life's a bowl of punch so go ahead and Spike it!" -311
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#13 Old 05-03-2007, 12:10 PM
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EJ20 bore -ing :P

Hi Everyone,
I got a spare ej20 and pair of cylinder heads off of ebay for a crazy price. I have been researching this for a long time. I wouldn't use the stock cylinder walls for 100mm pistons in the ej20. I'd use 98mm and get the legacy pistons if you aren't going to sleeve the block. I'm sure the 22B was basically a ej20 with 98mm pistons. You'd get around a 2.2L with that anyways With the block apart, I'm planning on installing darton sleeves (100mm). I'm also going to have a machine shop reinforce the quadrants of the cylinder walls like the sti block The top of the sti piston would affect the CR with the stock wrx rods and crank. I like the stock wrx rods because they are a bit shorter. I heard that shorter rods are easier to revv up as opposed to longer (sti) ones. If you use the stock wrx crank (I'd modify it for better oiling, so it has two oiling holes like the sti one) with the stock wrx rods (well dimensions anways, I'm going with pauter or eagle )and custom 100mm (wrx spec, with different quench area) pistons, then that should get you a 2.29 liter with 8 or 8.5:1 compression I'm also going to get 15mm head studs put into the block. I will get my GT35R d@mmit :P If I make any headway I'll post again. Its been about 4 months since my girlfriend of 4 years and I broke up and now I have some money to mod again I knew I had money somewhere

Craig, Pilot of a 2002 WRX 5MT, aka "Wookie" :P
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#14 Old 05-06-2007, 09:23 PM
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Sorry about the ex g/f... we all know girls are money pits. Anyways sounds like you have a sick build in mind. What turbo are you gonna slap on are you gonna run the stockie trans with the increase in torque ?
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#15 Old 05-06-2007, 09:32 PM
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Wow you really thought that put, bravo. How much did/would it cost to have said machine shop reinforce the cylinders, very interesting.
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