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Discussion Starter #1
I have finally planned the future of my 2000 2.5

I am going to get the motor rebuilt/BUILT. My goal is to stay N/A but walk those STIs that are going to be flooding the streets.

I am thinking I will need: Roller Cams, Head work including larger valves and decked possibly ported but not polished. I believe that polished surfaces are good for NASCAR when you run wide open all day. But, a nice bead blast surface surface is good for fuel atomization and mid range power. My target power band is 3-6000 but I am flexible.

How much can you bore a 2.5 before the block is no good for future rebuild?

What crank, rods and pistons are the best?

Throttle body and fuel system?

Do they make an aftermarket intake yet?

I would really appreciate some insight...I would like to spend less than 10,000
 

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13 Years of RS
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IMPREZA2000 said:
I am going to get the motor rebuilt/BUILT. My goal is to stay N/A but walk those STIs that are going to be flooding the streets...I would like to spend less than 10,000
Sorry to say it, but I don't think you are going to be able to get to 270+ hp NA for $10K. Just buliding up everything in the engine to reach those levels will be very expensive, and then you will have to worry about the gearbox. As to how far the EJ25 block can be bore out, I've heard of people going up to 2.7L, but I don't know how much that leaves for futere rebuilds.
 

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Discussion Starter #3
I should have been more specific. 10k is for the engine. I am figuring another 5k for drivetrain and 2k for fuel delivery and other little things that pop up. My wife says I can spend 15k but I can always add a couple grand somewhere.

That brings up another question..... I want a bulletproof transmission and rear diff. Anybody know where I can find the best price on these things.

I dont want to have a pissing match about how much everything is going to cost. I just thought you could help me out with some of the questions I had.

Mainly the crank, rods, pistons, roller cams, rockers, valvetrain, and head work. I either want to buy a new intake manifold or have my stock one extrude honed. I will need a throttle body, fuel pump/ rail, injectors, and whatever but I want to start with the engine internals.
 
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IMPREZA2000 said:
I have finally planned the future of my 2000 2.5
How much can you bore a 2.5 before the block is no good for future rebuild?
The knight motorsports rally car is broed and/or stroked (not sure) to 2.7L and has no problems running 480+ forced induction HP and a 9,000 RPM redline with Motec management.

Very much looking forward to what you come up with, my dream is to have a 280+ HP N/A car. Glad to see someone who isn't married to forced induction!
 

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13 Years of RS
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IMPREZA2000 said:
I should have been more specific. 10k is for the engine. I am figuring another 5k for drivetrain and 2k for fuel delivery and other little things that pop up. My wife says I can spend 15k but I can always add a couple grand somewhere.

That brings up another question..... I want a bulletproof transmission and rear diff. Anybody know where I can find the best price on these things.

I dont want to have a pissing match about how much everything is going to cost. I just thought you could help me out with some of the questions I had.

Mainly the crank, rods, pistons, roller cams, rockers, valvetrain, and head work. I either want to buy a new intake manifold or have my stock one extrude honed. I will need a throttle body, fuel pump/ rail, injectors, and whatever but I want to start with the engine internals.

Oh, I thought the $10k was for everything, not just the motor. For the gearbox, check out the Chalek set on www.imprezars.com , a sychro'd gearset that can handle up to 450 HP, I believe. You would need to get a Phase I transmission case for it, I think, but that should be pretty easy. Don't know what to tell you about the rear dif, though, don't know of any replacements for it. But, then again, I've heard of people running lots of power through the stock one without problems, so that might not be necessary. For all the engine goodies, the only place I know that has them is www.cobbtuning.com , but I know there are other places out there, I just can't remember them off the top of my head. Maybe Paeco, but I don't know if thier website is thier name or not. Might snoop around on Primm Motorsports site, they have all sorts of stuff, but I'm not sure if they have what you are looking for. And I wan't trying to rain on you parade with my first post, just didn't know the amount you quoted was for just the engine. Good luck on the project, gotta love an NA monster!
 

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Paeco sells the 2.7 stroker kit for our cars. But I have never purchased anything from them. I believe JUN also sells a 2.7 kit although I'm not real sure on this one.

JUN, Cobb and TWE have cams for our cars.

Farm out the head work to somebody who knows our cars well.

Might want to up the compression to 11:1 or 12:1.

Rods and crank should be plenty strong for 270 Hp. Pistons will have to be replaced.

Knife edge the crank.

Extrude hone your intake.

Have your throttle body bored out an additional 3mm - 5mm.

Parallel Fuel rail mod

Motec, Link, TEC-3, etc...for fuel management



Not to sure about the stock injectors. To save a little money you could add an additional injector to your throttle body for increased fuel.


Just throwing stuff out there... :D
 

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yes like the others have said, knife edge crank.

might want to get some very light pistons and rods.

What was that one company that does Carbon fiber rods and pistons for Posches called? They might be able to get...err i mean, make you some... It's Carbon on the inside and some type of coating on the outside. Very nice and race proven.....(i think from what i remembered)

I'll try to find the site, then come back to you....

FuJi

I've found the site for the Carbon Pistions but the site don't work anymore.
Carbon talk

I dunno if you'd want Carbon pistions but they do benifit less weight. Anyway....that's all i wanted to say.
 

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Discussion Starter #8
I finally looked at cobbtuning.com I really like they're stage 2 shortblock and stage 2 heads. I sent them an email about estimated HP with both of them. Only thing I dont like is having to pay over 2k in core charges. I can not seem to find a roller cam or rocker arms anywhere but, that cobb setup looks tasty. I cant wait to hear from them......... I hope its good on the HP numbers.

Keep all the help coming I need all the tips I can get.
 

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The cobb cams are already roller because the stock cams are roller as are the rocker arms. Pretty nifty stock setup.

You might be able to take the rockers to someone and have them create a lighter set for you.
 

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i know it's an ego thing to stay N/A, but why the reluctance to turbo? you can get power as reliable for way less... a 4 banger with that much N/A power will need rebuilds fairly often is my guess...

on another note, you can get diffs from www.rallispec.com or cobb sells sti and quaffe (sp?) or at least used to...
 
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To boost or not to boost, that's the question

DanzBorin said:
i know it's an ego thing to stay N/A, but why the reluctance to turbo? you can get power as reliable for way less... a 4 banger with that much N/A power will need rebuilds fairly often is my guess...
I don't mean to contradict you, but power as reliable? With a turbo there *can* be worry of boost spikes or shattered impeller schrapnel getting sucked into the motor, among other possible catastrophic events. Isn't crank driven supercharging more "reliable" than turbocharging despite the downsides? It seems to me a 270 HP N/A motor has to create equal pressures in the cumbustion chamber as a 270 HP force fed motor. Are not the same forces present in either case to produce the same amount of force on the crank? It would aslo seem to me that producing that power by increasing flow, displacement and compression would be inherently more reliable just by reducing the number of moving parts. (no compressor)

There is a statistical law (that I'm not very versed on) that dictates the chance of failure on any machine is proportional to the amount of parts in that machine.
 

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Re: To boost or not to boost, that's the question

ampsarus said:
I don't mean to contradict you, but power as reliable? With a turbo there *can* be worry of boost spikes or shattered impeller schrapnel getting sucked into the motor, among other possible catastrophic events. Isn't crank driven supercharging more "reliable" than turbocharging despite the downsides? It seems to me a 270 HP N/A motor has to create equal pressures in the cumbustion chamber as a 270 HP force fed motor. Are not the same forces present in either case to produce the same amount of force on the crank? It would aslo seem to me that producing that power by increasing flow, displacement and compression would be inherently more reliable just by reducing the number of moving parts. (no compressor)

There is a statistical law (that I'm not very versed on) that dictates the chance of failure on any machine is proportional to the amount of parts in that machine.
yes, turbos can cause problems... but looking aside of imperfections (turbo shrapnel...) if tuned correctly should run more reliably...

supercharging has not seemed to fair well for the RS

putting out that kind of power in a NA tuned 4 banger takes lots of work, and running a higher redline, therefore causing problems...

nobody really knows how well it will hold up as nobody seems to have done it, whereas i know lots people are running this kind of power turboed
 
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The only supercharged Impreza I have seen and/or driven is ARG's 99' AutoRotor based Rimmer. It pulls in 5th to redline like my stock 00' pulls in 3rd. He has been running the S/C on his car for 20K+ miles. The only engine problems he has had with the kit is getting it to idle properly with the OBD-II. (he is a compitent mechanic) His 5-speed is pretty worked though, and makes unhappy noises. Some people have had trouble getting the Rimmer kit to run in thier car at all and ended up shelving the thing. This may be an installer issue and not a supercharger issue. The majority of the negative supercharger experiences revolves around the fact that they paid for a Rimmer kit and never got one. The guy ripped off people and this in itself has cast a dark shadow on supercharged Imprezas. I'm confident Kent at DNT will lift this dogma with his centrifugal kit and we will see many happy supercharged Impreza owners in the future. :)
 

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IMPREZA2000 said:
I am thinking I will need: Roller Cams, Head work including larger valves and decked possibly ported but not polished
As already pointed out, the stock valvetrain is a full roller valvetrain, so there's probably not much to gain there. Having someone custom-make some lighter roller rockers would cost some serious $$$ methinks.

Same thing goes for the larger valves. Considering how few shops there are that really seem to have done their homework on the Subaru heads (namely, Cobb Tuning) you're kinda stuck with who you can go with. Cobb's heads are expensive to begin with, adding in even more work to deck the heads, work the chambers to fit larger valves, and then actually get the larger valves (more custom work?) = $$$.

IMPREZA2000 said:
My target power band is 3-6000 but I am flexible.
You'll need to go well above 6000rpm to make 270hp. A stock 2.5L doesn't even hit peak power until 5600rpm, if you want to achieve about a 165% increase in power output you're going to need to have your powerband in the VTEC range. :) Of course, to do that will require some sort of aftermarket engine management - did I mention $$$?

IMPREZA2000 said:
How much can you bore a 2.5 before the block is no good for future rebuild?
Not much. I want to say it's only like 1mm or 1.5mm, something like that.

IMPREZA2000 said:
Throttle body and fuel system?

Do they make an aftermarket intake yet?
Extrude Honing the stock intake isn't going to be anywhere near enough to make the kind of power you want. It's a weakness of the flat engine design - the intake manifold ends up having loooong runners, which is great for torque (no surprise there) but sucks for top end power. Eventually someone is going to need to develop a dual or individual throttle body setup if any of us wants to really explore the limits of these engines. Once again, $$$$.

I'm not trying to rain on your parade, just injecting some reality. I've already spent plenty of money on my car (Cobb Stage 1 heads, Street/Stage 1 cams, MRT full exhaust, Fidanza flywheel, Injen intake, and S-AFC) and I'm making around 205hp, maybe 210hp. I'm sure there's more power to be had with my current combo but it would require some sort of aftermarket engine management and dyno tuning - someday I'll get around to that. I definitely don't think there's another 60+hp to be had just with tuning - that would require more aggressive cams, more port work on the heads, some sort of new intake system, and a higher redline.

Good luck!
Pat Olsen
'97 Legacy 2.5GT sedan
 
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Re: Re: 270+ Hp Rebuild?

Patrick Olsen said:


Eventually someone is going to need to develop a dual or individual throttle body setup if any of us wants to really explore the limits of these engines.

I definitely don't think there's another 60+hp to be had just with tuning -
Multiple throttle bodies- What a great idea. Why would it be so difficult/expensive? Couldn't one make wooden left and right side single runner manifolds with a lathe and mill, then have some clones cast in aluminum? I bet if I was still in high school I could do it in metal shop! :)

I think I read on Cobbs site that the Subaru stock heads flow really well, and that there isn't much that can be done to improve on them.

Would an increase in compression, say to 11.5:1 with an aftermarket ECU make the extra 60+ HP? Gas might be a problem for most people; I can get 76 or Trick 100 octane unleaded in this area. It ain't cheap, but even my stock RS runs much smoother on it.
 

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$15K? Just saw a guy in Chicago is importing 2004 STi Engines, along with the 6 speed for $12K. Problem solved.

N/A? Yeah, I'd cry about the turbo whine evertime I stuck it in 6th gear.:rolleyes:
 

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Hey everyone, I sent my engine to a very good machine shop through lachute subaru www.lachutesubaru.com to have every part of it built up for as much N/A power as possible. I sent it in after damaging my engine with a nitrous dry kit when i had ported and polished heads and intake manifold and cobb's spicy cams along with all the other bolt ons. I broke a valve the first time and residual damage fromt the nitrous after it was fixed made me throw a connecting rod bearing so that was what made me decide to do this. Heres the mods:

Stromung cat back
Random tech hi flow cat
Borla headers
Cobb CAI
UD pulley
Ported and polished cylinder heads
Ported and polished intake manifold
Cobb Spicy cams
Cobb valve springs
Cobb titanium retainers
Custom stainless steel valves
Closed deck bock
11:1 compression pistons nitrous coated
custom connecting rods (length increased by 4mm)
knife edged crank shaft
balanced
blueprinted
Sleeved
ACT street clutch
9lb or 9.5lb flywheel
STi engine mounts
STi tranny mounts
Unichip engine management
NX 4 fogger nitrous kit 50 shot (used to have a zex dry)
Redline set at 8,000 rpm

I would like any input you guys have for me! The engine comes back to me before the end of the month. Im also working on a custom intake manifold with my brother which uses two throttle bodies. and I need to extrude hone my throttle body in the mean time. Thanks for any input guys!

Dan

:)
 
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dcoty said:
........after damaging my engine with a nitrous dry kit ......(used to have a zex dry)
Looks like you are going to have a sweet motor when it's done.
Any figures on how much power it will produce?

How much N20 were you running with the Zex when your motor blew? I'm wondering if it was a fuel enrichment issue? I'm considering a Zex kit, any additional info would be very useful.
Thanks
 

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We figure around 250 hp, more when I build a new intake manifold with my brother which uses twin throttle bodies, thenIll see more hp for sure, the intakme mnaifold is the weak point on our cars.

I was only using a 50 shot from the dry kit. It worked great with just cobbs street cams in my car and all the other bolt ons (except for a slipping clutch). But when i added the ported/polished heads and intake manifold and cobb spicy cams, the car flew...for 1 klm, then in fourth I got detonation and broke the valve. Even with an upgraded fuel pump, the engine did not get enough fuel and the fuel injectors got stuck open, melted 3 spark plugs and broke the valve.

Now I am getting a wet kit, and I would reccomend you to stay away from a dry kit, wet kits are not much more expensive and its way safer. But if you are running stock internals (mild cams are fine) then go with the Zex kit, i really loved mine, you wanna buy it?
Dan:)
 
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