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Old 02-18-2008, 11:37 PM   #1
wrxwagon253
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Default Hybrid Wagon Build using stock Wrx heads on Sti 2.5L block

Im just getting started with my build and am looking for any pointers or advice one might have from their own previous experience.. I will be using stock wrx heads on the sti block mated to a 6spd tranny,aluminum driveshaft and a 3.90 r160 rear diff. I read that I can use a specific cometic headgasket to keep the compression ratio as close to stock as possible.I have more questions but for now just looking for advice or tips to make it go as smoothly as possible.. Thanks
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Old 02-19-2008, 12:08 AM   #2
kellygnsd
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Please read and search the many hydrid builds going on exactly like yours. Some are even on the first page
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Old 02-19-2008, 02:21 AM   #3
wrxwagon253
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I did
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Old 02-19-2008, 01:25 PM   #4
Paulys05wrx
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I am in the process as we speak, on a 2005 WRX. It should be all done by this weekend! As far as the head gasket... I stuck with the stock STI head gasket because from my experiences I really don't like messing with the CR by changing head gasket size. But many people on here have used the cometic with good success. The thing is the STI head gasket wont totally mess up your CR, it just raises it a bit so the tuner will have more work. I'm curious to see how this build goes. I'll try to check in and help out
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Old 02-19-2008, 01:28 PM   #5
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Quote:
Originally Posted by wrxwagon253 View Post
I have more questions but for now just looking for advice or tips to make it go as smoothly as possible..
Forgot to give you some advice... Main thing is take your time!! Be patient and everything will go smooth.
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Old 02-19-2008, 01:46 PM   #6
Turbo_Mike
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Agreed, dont mess with head gaskets, thats the least of your issues. Stock STi ones are totally fine for way more power and boost than the heads can handle. The main issue with the 2.5 hybrid is that the combustion chamber on the head side doesnt match the cylinder side because the 2.0 bore is smaller, which makes it more detonation prone than sti heads, and the 2.0 heads really dont flow enough to make high rpm power, especially with stock cams. Its still a HUGE upgrade from a stock 2.0....

My setup made 417hp/471tq at the wheels with a FP green and meth on my hybrid 2.5....
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Old 02-19-2008, 06:30 PM   #7
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You do realize what you have to modify for an aluminium driveshaft right? You will actually have to get under your car with a sledge and beat out the tunnel for given flex in the shaft. Not a real great idea, get an sti shaft or auto wrx.
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Old 02-19-2008, 08:52 PM   #8
wrxwagon253
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Quote:
Originally Posted by 2ndGearFling View Post
You do realize what you have to modify for an aluminium driveshaft right? You will actually have to get under your car with a sledge and beat out the tunnel for given flex in the shaft. Not a real great idea, get an sti shaft or auto wrx.
Yeah Ive done my research on that..And its minor work to modify for the aluminum driveshaft..No biggie..
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Old 02-19-2008, 09:08 PM   #9
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Are you guys using the stock WRX tmic on these hybrids or do you need to upsize to an STI tmic (or other) to handle increased airflow?
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Old 02-20-2008, 02:54 AM   #10
wrxwagon253
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Quote:
Originally Posted by manxaru View Post
Are you guys using the stock WRX tmic on these hybrids or do you need to upsize to an STI tmic (or other) to handle increased airflow?
Im using a greddy Fmic kit and would recomend using a Sti Tmic at the least depending on the turbo you decide to use..
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Old 02-20-2008, 10:10 AM   #11
Turbo_Mike
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The stock TMIC is definately not a good idea unless you run stock turbo and stock boost. Its not a performance unit, at all.
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Old 02-20-2008, 04:29 PM   #12
wrxwagon253
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SO does anyone have any input on using the sti cams in my wrx heads? Ive heard the wrx heads flow crappy on th e2.5 block and the power falls off around 5k is this true? Am I able to simply plug the avcs holes and install them in my wrx heads with stock valvetrain or should I upgrade valvetrain at the same time..Im kinda strapped for cash after buying the tranny and driveline and some other misc. parts..Any input would be nice..Thanks again guys..
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Old 02-20-2008, 05:01 PM   #13
kellygnsd
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There's a how-to two post above showing how to do just what you ask. Search is you friend but since it was on the first page that wasn't even necessary
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Old 02-20-2008, 05:51 PM   #14
paintbing
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I assume that you spun a bearing, and are using it as an excuse to upgrade?
Well, if that's the case, don't try to "save" money by re-using your oil cooler. just replace it, and save yourself from receiving a clogged oil passage and destroyed head. That is my best advice that I can give you.
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Old 02-20-2008, 05:54 PM   #15
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Quote:
Originally Posted by wrxwagon253 View Post
SO does anyone have any input on using the sti cams in my wrx heads? Ive heard the wrx heads flow crappy on th e2.5 block and the power falls off around 5k is this true? Am I able to simply plug the avcs holes and install them in my wrx heads with stock valvetrain or should I upgrade valvetrain at the same time..Im kinda strapped for cash after buying the tranny and driveline and some other misc. parts..Any input would be nice..Thanks again guys..
Much info on this as well. You must plug the AVCS holes on the intake cams. They will bolt right up as well. You "should" get the STI cam seals for the two intake cams, but use WRX seals for the exhaust cams. Most people upgrade to STI cams for one reason only... so that you can have more power on the top end. Good luck!
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Old 02-20-2008, 11:35 PM   #16
wrxwagon253
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Quote:
Originally Posted by kellygnsd View Post
There's a how-to two post above showing how to do just what you ask. Search is you friend but since it was on the first page that wasn't even necessary
dude would you ****..I am researching before asking questions and everyone is giving me answers but you, who is giving me ****..If you dont have some solid input about a question I ask dont waste space on my thread..Thanks to you that have offered me info..
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Old 02-20-2008, 11:46 PM   #17
kellygnsd
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Then don't waist bandwith on the board when the answer is right on the first ****ing page. Even without a search a quick scan of the first page of built motor discussion would have answered you STi cam question. The whole first page is all hybrid builds exactly like yours so instead of answering the same question 1 million times open you eyes or at least look to see what has been posted recently.
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Old 02-21-2008, 12:55 AM   #18
wrxwagon253
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Quote:
Originally Posted by kellygnsd View Post
Then don't waist bandwith on the board when the answer is right on the first ****ing page. Even without a search a quick scan of the first page of built motor discussion would have answered you STi cam question. The whole first page is all hybrid builds exactly like yours so instead of answering the same question 1 million times open you eyes or at least look to see what has been posted recently.
Instead of letting this turn into a bitchfest ill set you straight..I read that post and nobody spoke on the stock valvetrain being used with it so I asked.Is that such a big inconvenience to you..Get a life..I also asked the same question in that thread and now I have the answer im looking for..People like you should mind there own business..
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Old 02-22-2008, 02:38 PM   #19
Spec V to Wagon
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if you serach for my name I made a how to for sti cams in wrx heads. I used them when I did my hybrid build in my wagon.

I also wouldn't mess with head gaskets but that is a choice you have.
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Old 02-22-2008, 03:46 PM   #20
wrxwagon253
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Quote:
Originally Posted by Spec V to Wagon View Post
if you serach for my name I made a how to for sti cams in wrx heads. I used them when I did my hybrid build in my wagon.

I also wouldn't mess with head gaskets but that is a choice you have.
So do you recommend using stock sti headgaskets then?
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Old 02-22-2008, 03:53 PM   #21
Spec V to Wagon
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Quote:
Originally Posted by wrxwagon253 View Post
So do you recommend using stock sti headgaskets then?

Just buy the engine overhaul kit for a 2.5 and make sure you get the 2.0 valve cover gaskets. I mean some people used the cometic head gaskets to try and keep the CR down. I think with the 2.5 gasket CR is up to like 8.8 or 8.9. To me that didn't matter. But some will argue till no end.

I got all my parts from tristan at TheKingofParts.com, they had the best prices I could find.
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Old 02-22-2008, 07:21 PM   #22
wrxwagon253
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Quote:
Originally Posted by Spec V to Wagon View Post
Just buy the engine overhaul kit for a 2.5 and make sure you get the 2.0 valve cover gaskets. I mean some people used the cometic head gaskets to try and keep the CR down. I think with the 2.5 gasket CR is up to like 8.8 or 8.9. To me that didn't matter. But some will argue till no end.

I got all my parts from tristan at TheKingofParts.com, they had the best prices I could find.

Im looking to keep my CR as close to stock as possible..I want this to be daily driven and as reliable as possible. I've been told that when raising the CR its more of a task for my tuner..Not that im worried about Tim Bailey's tuning or anything its just I guess id like the piece of mind..lIm looking to make good power but not at the cost of reliability. What do you suggest?
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Old 02-22-2008, 07:41 PM   #23
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Quote:
Originally Posted by wrxwagon253 View Post
Im looking to keep my CR as close to stock as possible..I want this to be daily driven and as reliable as possible. I've been told that when raising the CR its more of a task for my tuner..Not that im worried about Tim Bailey's tuning or anything its just I guess id like the piece of mind..lIm looking to make good power but not at the cost of reliability. What do you suggest?
If your tuner is good then tuning for a higher cr should be no problem. A higher cr makes for a great daily driver because there is more response in off boost driving situations plus you get the added bonus of a wider torque band. Another thing you might want to do is drop in a set of forged pistons. I highly recommed this because I am rebuiding my hybrid motor now because of low compression on 3 cylinders with the stock EJ257 sb. The rings failed. The added cost isn't very high and the reliability is increase significantly.
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Old 02-22-2008, 09:14 PM   #24
wrxwagon253
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Quote:
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If your tuner is good then tuning for a higher cr should be no problem. A higher cr makes for a great daily driver because there is more response in off boost driving situations plus you get the added bonus of a wider torque band. Another thing you might want to do is drop in a set of forged pistons. I highly recommed this because I am rebuiding my hybrid motor now because of low compression on 3 cylinders with the stock EJ257 sb. The rings failed. The added cost isn't very high and the reliability is increase significantly.
Yeah I decided that I will go with aftermarket pistons just not sure which ones..I dont want the engine to be noisy which ive been told some aftermarket pistons can cause. Ive heard good things about the CP pistons so I think that will be my choice..As far as I know the stock rods are fine but the stock pistons like to crack under det. and the ringlands have problems..Ill talk to my tuner and see what he recommends for headgaskets since ive been getting mixed answers about using stock or cometic..Thanks for your help and good luck with your build..
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Old 02-23-2008, 07:10 PM   #25
Spec V to Wagon
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Quote:
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Yeah I decided that I will go with aftermarket pistons just not sure which ones..I dont want the engine to be noisy which ive been told some aftermarket pistons can cause. Ive heard good things about the CP pistons so I think that will be my choice..As far as I know the stock rods are fine but the stock pistons like to crack under det. and the ringlands have problems..Ill talk to my tuner and see what he recommends for headgaskets since ive been getting mixed answers about using stock or cometic..Thanks for your help and good luck with your build..
At this point just go Axis stage 2.
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