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Old 10-01-2007, 12:14 AM   #1
n2oiroc
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Default engine build advice!

so i blew the ringlands on cylinder #4 on my element gt49 equipped 07 sti and have a few questions about building a new shortblock. i want the new one to be bulletproof for constant 500whp beatings. mine is already trashed with 7,000 total miles and 2,000 since the turbo upgrade. i dont want to do this again!

1. are the 06 and earlier short blocks directly interchangeable with the 07?
2. what is everyone using for rings and bearings?
3. anything else i should upgrade besides pistons and rods?
4. anything else to do while its apart? i already plan on tgv deletes and maybe porting the heads a little.
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Old 10-01-2007, 12:26 AM   #2
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IIRC the 07 sti's have a smaller combustion chamber, so any 04-06 sti shortblock pistons would yield a higher CR....be sure to do the math on that. Aside from that, the rods, crank and block are all interchangable.

Rings and bearings: Any aftermarket ring should have no issues at 500whp. As for bearings, I've never gone wrong with ACL coated and am going to run a acl h-series with a calico coating on my upcoming build.

Rod and pistons: upgrading them with the bearings and rings (will come with the pistons) should be fine, as you are already doing bearings. I would upgrade to a 12mm pump or a massaged 10mm pump for added security and the ability to rev higher if you choose to do headwork down the road.

I would deck the block and toss in a cometic HG and some ARP studs for insurance.
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Old 10-01-2007, 12:40 AM   #3
n2oiroc
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Quote:
Originally Posted by Homemade WRX View Post
IIRC the 07 sti's have a smaller combustion chamber, so any 04-06 sti shortblock pistons would yield a higher CR....be sure to do the math on that. Aside from that, the rods, crank and block are all interchangable.

Rings and bearings: Any aftermarket ring should have no issues at 500whp. As for bearings, I've never gone wrong with ACL coated and am going to run a acl h-series with a calico coating on my upcoming build.

Rod and pistons: upgrading them with the bearings and rings (will come with the pistons) should be fine, as you are already doing bearings. I would upgrade to a 12mm pump or a massaged 10mm pump for added security and the ability to rev higher if you choose to do headwork down the road.



I would deck the block and toss in a cometic HG and some ARP studs for insurance.
ok, so i can use all 04-06 parts except pistons correct? tgv housings are different too arent they? how much power and rpm is the stock crank good for? thanks!
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Old 10-01-2007, 02:09 AM   #4
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alright, seeing that there arent any good shops around here, i might just have axis or arfab build mine.

Last edited by n2oiroc; 10-01-2007 at 03:11 AM.
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Old 10-01-2007, 08:53 AM   #5
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yeah, you can have any of the builders do a motor for you. If you don't mind me asking. what do you do with the moto? daily drive, tracl, auto-x, drag...?
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Old 10-01-2007, 08:58 AM   #6
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if you have it honed, have it torque plated then honed/bored.
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Old 10-01-2007, 10:28 AM   #7
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Quote:
Originally Posted by Homemade WRX View Post
yeah, you can have any of the builders do a motor for you. If you don't mind me asking. what do you do with the moto? daily drive, tracl, auto-x, drag...?
3 season daily driver, occasional dragstrip and general daily beatings. im not easy on it, thats pretty obvious!
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Old 10-01-2007, 10:36 AM   #8
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ddddddddddddd
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Old 10-01-2007, 11:11 AM   #9
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but most of your fun driving is mid to top end power...short of putting around town...?
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Old 10-01-2007, 11:42 AM   #10
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I would go stock gaskets + arp rods. I've seen too many high quality builds go down the drain when they pop out an aftermarket HG.

I'd use Cosworth mains and ends and definitely look into replacing the valvetrain. Floating a valve is no fun and STI's seem to do it quite perpetually. I'd get either Ferrea Springs/Retainers or a Crower set.
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Old 10-01-2007, 02:02 PM   #11
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Quote:
Originally Posted by Homemade WRX View Post
IIRC the 07 sti's have a smaller combustion chamber, so any 04-06 sti shortblock pistons would yield a higher CR....be sure to do the math on that. Aside from that, the rods, crank and block are all interchangable.

Rings and bearings: Any aftermarket ring should have no issues at 500whp. As for bearings, I've never gone wrong with ACL coated and am going to run a acl h-series with a calico coating on my upcoming build.

Rod and pistons: upgrading them with the bearings and rings (will come with the pistons) should be fine, as you are already doing bearings. I would upgrade to a 12mm pump or a massaged 10mm pump for added security and the ability to rev higher if you choose to do headwork down the road.

I would deck the block and toss in a cometic HG and some ARP studs for insurance.

What is the CC volume of the 07 pistons and combustion chambers ?
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Old 10-01-2007, 02:43 PM   #12
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I'm not sure, nor have I cc'ed themself. I was told this and haven't seen any numbers for it.
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Old 10-01-2007, 02:46 PM   #13
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told by who?
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Old 10-01-2007, 02:53 PM   #14
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Quote:
Originally Posted by Homemade WRX View Post
but most of your fun driving is mid to top end power...short of putting around town...?
i never really putt around town, ill be the first to admit. after its warmed up it gets flogged to redline daily. i do maintain it very good though.
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Old 10-01-2007, 03:19 PM   #15
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Quote:
Originally Posted by Homemade WRX View Post
I'm not sure, nor have I cc'ed themself. I was told this and haven't seen any numbers for it.
That was my assumption...

I have seen many 07's come through my pops shop and the CC volume of the cylinder heads are the same as the earlier STI heads.
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Old 10-01-2007, 09:52 PM   #16
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Default Third Post to ask a question....

It sucks when you have to rebuild your motor!! I just spun a rod bearing on my 05.....
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Old 10-01-2007, 09:59 PM   #17
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Quote:
Originally Posted by bjpeppers View Post
It sucks when you have to rebuild your motor!! I just spun a rod bearing on my 05.....
at least it isnt "that" expensive to rebuild one. it could be much worse.
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Old 11-19-2007, 01:40 AM   #18
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Total newb question - sorry - but what makes the compression ratio in a motor? The pistons?

An '07 STI short block with 04-06 STI pistons would yield a higher compression ratio, right?

A built EJ257 motor (Cobb, Cosworth, Crawford, Axis, AR Fab... whoever) for any year STI would have the same compression ratio depending on the pistons used?

<---- In the market
Thanks guys
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Old 11-19-2007, 02:01 AM   #19
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many things can influence the CR of your motor.

you need the measurements of the following to determine your comp. ratio:

crankshaft stroke
cylinder bore
piston dish
gasket bore
gasket thickness
rod length
and i forget the term (if piston pops out of the hole or not)

i think thats it.


~Josh~
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