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Old 07-30-2003, 08:57 PM   #1
serious
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Default 2.5 sti block with 2.0 regular wrx heads

Hi all, i know some of you out there have done this already or at least something similar. What i would like to know is what it would take to get the new sti 2.5 block to work properly with the 2.0 heads?
Would i be able to use a uni chip with this or would i have to buy something like the utec? What compression ratio would it have and would everything line up like it should?
Thanks
Brent
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Old 07-30-2003, 10:23 PM   #2
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I think you're better off with some 2.5 heads, they breath so much better (better than LS1 heads believe it or not! )
But thats what I would do...
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Old 07-30-2003, 10:53 PM   #3
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well I dont know about the rs ej25 heads.... but if you use a 2.5 block with us wrx heads you would have a motor great for a truck.

the low flow rates and the low deration cams would make great tq down low but no power up top. The motor would be useless after like 5k...

get some sti v7 or v8 heads.... they have longer deration cams then the us. I dont remeber the numbers but im sure there around here somewhere.
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Old 07-31-2003, 12:21 AM   #4
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Lets say i really really wanted to use my usdm wrx 2.0 heads. Could i install a head package that would equal the sti heads or maybe better it?
Thanks
Brent
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Old 07-31-2003, 12:27 AM   #5
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Quote:
Originally posted by serious
Lets say i really really wanted to use my usdm wrx 2.0 heads. Could i install a head package that would equal the sti heads or maybe better it?
Thanks
Brent

Waste of money... For the money involved, you could just get the STi heads and have it installed... and have some cash left over
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Old 07-31-2003, 02:48 AM   #6
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Quote:
Originally posted by kastle



Waste of money... For the money involved, you could just get the STi heads and have it installed... and have some cash left over
i disargree

try to get an STi head to flow as well as a ported head with oversized valves and higher lift cams.

but in the end you are gonna spend $3g's on head work.

Jeremy
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Old 07-31-2003, 03:54 AM   #7
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I think Stealth-wrx is running this setup ... see what he thinks of it..
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Old 07-31-2003, 04:53 AM   #8
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Quote:
Originally posted by HOK
I think Stealth-wrx is running this setup ... see what he thinks of it..

I dont know if his heads are reworked.... but I know hes looking for better cams.

and as for it being a wast of money... if you know good shop you trust then maybe not.
I would just get new sti heads I dont think youll need more flow then they will give you and they come with cams... no need to mess with grinded or welded
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Old 07-31-2003, 11:29 AM   #9
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Quote:
Originally posted by totoherbs



I dont know if his heads are reworked.... but I know hes looking for better cams.

and as for it being a wast of money... if you know good shop you trust then maybe not.
I would just get new sti heads I dont think youll need more flow then they will give you and they come with cams... no need to mess with grinded or welded
don't forget that the cams and heads are designed for emissions purposes, therefore you CAN get more flow out of a different head. If you have seen the work i have you wouldn't be so impressed with the STi heads.

Jeremy
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Old 07-31-2003, 01:50 PM   #10
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I think it was the Type RA Spec C heads, in particular, that had the huge ports. I'm not so sure that the other STi's had such large ports.

I don't know how much the STi heads are going for, but you can have Cobb heads for $4k including completely redone valvetrain and cams. I guess it all depends how much power you are going for.

Since the bore is going to be different, you would also want to massage your combustion chamber on the heads to match up well.

-Jon
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Old 07-31-2003, 03:27 PM   #11
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Thanks for the response. Ultamately i'm going for a good horsepower and TORQUE combination. I would still like to have a decent top end but would be willing to sacarifice a little up high to get some good low to mid range grunt stomp the pedal and go power.
I would like to work with the wrx heads as i already have them and all that i need to install them with. Then again i have two 2.2 turbo engines just sitting in my garage. I would rather go with a larger displacement engine if i can and one with a good aftermarket/technical support.
Brent
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Old 07-31-2003, 11:04 PM   #12
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Quote:
Originally posted by stimpy
I think it was the Type RA Spec C heads, in particular, that had the huge ports. I'm not so sure that the other STi's had such large ports.

I don't know how much the STi heads are going for, but you can have Cobb heads for $4k including completely redone valvetrain and cams. I guess it all depends how much power you are going for.

Since the bore is going to be different, you would also want to massage your combustion chamber on the heads to match up well.

-Jon
The only difference between the sti heads and the spec c's are the intake manifold risers and longer deration cams.... the ports are the same size. You can get low mileage cams for 1300 to 1500 and an ecu+harnes is like 850, which you would need to get the cams to work.

Quote:
don't forget that the cams and heads are designed for emissions purposes, therefore you CAN get more flow out of a different head. If you have seen the work i have you wouldn't be so impressed with the STi heads.
but for the same cost as the sti's?

Last edited by totoherbs; 07-31-2003 at 11:20 PM.
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Old 08-01-2003, 12:24 AM   #13
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[edited -- see below] Too bad I don't have an extra $2k to blow on my project or I could stuff some STi heads on there and make a little more power

-Jon

Last edited by stimpy; 08-01-2003 at 03:43 PM.
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Old 08-01-2003, 02:24 AM   #14
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Quote:
Originally posted by totoherbs


The only difference between the sti heads and the spec c's are the intake manifold risers and longer deration cams.... the ports are the same size. You can get low mileage cams for 1300 to 1500 and an ecu+harnes is like 850, which you would need to get the cams to work.



but for the same cost as the sti's?
considering you still have to purchase theheads, cams, ecu etc yes.

not to mention the peace of mind of NOT having to search far and wide for replacement parts/

Jeremy
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Old 08-01-2003, 03:45 PM   #15
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Quote:
Originally posted by totoherbs

The only difference between the sti heads and the spec c's are the intake manifold risers and longer deration cams.... the ports are the same size.
As per Clark's post:
Quote:
The JDM WRX and the V7 STI heads are the same save the cams. The Type RA heads for the V7 cars are based on those heads but have port work, Sodium filled valves and higher lift cams.
Another of Clark's posts:
Quote:
Not all V7 Ej207 STI engines have the same heads. Early exampls where simply V6 motors and used the older castings exactly like the US car. Later V7 STI engines came standard with the new updated large port heads. As a result they made more power.
So, there is not just one STi head.

-Jon

Last edited by stimpy; 08-01-2003 at 04:10 PM.
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Old 08-02-2003, 12:32 AM   #16
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I stand corrected

Theres lots of difference in sti heads ver 1 threw 6

Now if you want something realy nice get the S202 heads

The spec C is smoth hand ported... I think the ver 8s have the larger ports like the spec c, but there would be some wiring issues with then due to the new ecu



I know what you mean about finding replacment parts.

Last edited by totoherbs; 08-02-2003 at 12:55 AM.
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Old 08-02-2003, 12:54 AM   #17
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Sorry for the confusion; I was also referring to the V7/V8 heads. I know there are tons of differences between the other years.

Supposedly some of the new STi stuff is going to cause a problem with wiring since they may be using the 2004 style ecu and wiring harness. I was just reading about this earlier today.

-Jon
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Old 08-02-2003, 12:57 AM   #18
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Quote:
Originally posted by stimpy
Sorry for the confusion; I was also referring to the V7/V8 heads. I know there are tons of differences between the other years.

Supposedly some of the new STi stuff is going to cause a problem with wiring since they may be using the 2004 style ecu and wiring harness. I was just reading about this earlier today.

-Jon
Ya something about having change all the conecters.
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Old 08-02-2003, 02:05 AM   #19
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Quote:
Originally posted by serious
Thanks for the response. Ultamately i'm going for a good horsepower and TORQUE combination. I would still like to have a decent top end but would be willing to sacarifice a little up high to get some good low to mid range grunt stomp the pedal and go power.
I would like to work with the wrx heads as i already have them and all that i need to install them with. Then again i have two 2.2 turbo engines just sitting in my garage. I would rather go with a larger displacement engine if i can and one with a good aftermarket/technical support.
Brent
Here's my take on it....

If you're looking to make big power you need to flow alot of air, on either a EJ20 or EJ25. The standard wrx heads won't do it. Based on air flow, 14 psi on a 2.5 is equivalent to 22 psi on a 2.0 - so don't plan on running big boost to redline on WRX heads. I think something like 15 psi in the midrange, tapering to 13 psi at redline, would be a reasonable expectation for wrx heads, on pump gas. You could do this with a VF34, and this would give you a super huge powerband with full boost at 2500 RPM and very little lag, and maybe 350 crank hp - basicly an AWESOME street motor.

Kevin
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Old 08-02-2003, 04:27 PM   #20
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just a quick related question....anybody know the price of the new STi 2.5 Shortblock for sure?

Kyle
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Old 08-02-2003, 05:23 PM   #21
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I'm pretty sure once the new sti 2.5 block is for sale it will be priced at about 1500-1650 or so. I did know of a source a while back that had a lead and was selling for 1250. Yeah 1250. Then the price went up to 1350 or so because there was some problems getting them. Then all of a sudden he back out on taking any further orders for them.

Red Rocket: What combination are you talking about? The new sti 2.5 block matted to the usdm 2.0 heads?
Does anybody know for sure the specs like compression ratio and actuall displacement with this setup? Any possible problems that i could run into?
Thanks
Brent
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Old 08-03-2003, 12:36 PM   #22
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the Spec C heads don't have the separation for each valve in the intake port like all the other heads have.
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