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Old 09-06-2007, 11:06 AM   #1
wittmer25
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Default Difference between 04-06 USDM STi heads and 07 heads?

Are there any differences between these year model heads?
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Old 09-06-2007, 11:53 AM   #2
TAPOUT
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Yes. I don't know all the specifics, but I think the 07 heads have a smaller combustion chamber, and different cooling passages.
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Old 09-06-2007, 12:26 PM   #3
Jeremy@Cobb
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D25 cylinder head castings castings
- Added air injection
- 49.6cc combustion chamber
- Cooling passages, and most internal area of the casting is different to allow for the air injection.

- J.
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Old 09-06-2007, 01:26 PM   #4
wittmer25
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so my next question, are the 07 heads compatible with an earlier sti ej257 block?" i have heard of a block off plate for the air pump.
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Old 09-06-2007, 04:43 PM   #5
R & H Garage
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you'd need a custom piston. Otherwise your compression ratio will be around 9:1... if you don't want that.
I like 9:1.

Also, people with high HP 07's are showing cooling issues. Actual reason isn't known. It could be not enough flow in the heads or volume in the cooling system.
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Old 09-10-2007, 05:22 PM   #6
Wrinkleboi
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Quote:
Originally Posted by Jeremy@Cobb View Post
D25 cylinder head castings castings
- Added air injection
- 49.6cc combustion chamber
- Cooling passages, and most internal area of the casting is different to allow for the air injection.

- J.
can you explain what a D25 cylinder head casting is? or do you mean it actually says "D25" on the outside of the heads?
and how is the internal area different because of the air injection?

i put an 07 motor into my car and removed the air pump in the process to make room for other things. i also recently did a TGV delete and noticed the intake ports of the heads are very rough.



thread on the subject posted here: http://forums.nasioc.com/forums/show....php?t=1337066
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Old 09-11-2007, 06:02 PM   #7
Devan M
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Quote:
Originally Posted by KitoAutoSport View Post
you'd need a custom piston. Otherwise your compression ratio will be around 9:1... if you don't want that.
I like 9:1.

Also, people with high HP 07's are showing cooling issues. Actual reason isn't known. It could be not enough flow in the heads or volume in the cooling system.
Crawford stocks the custom components for the 07's that give you an 8.2 to 1 compression ratio.
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