2.0 WRX heads compaired to later 2.5 WRX heads is there any diferences ??

[gtrclive]

I'm going to buy a New 2.5 STI short block, and was going to reuse my 2002 WRX heads (With the JE Pistons to correct the Compression Issue),
have thought of getting a Set of used Late model 2.5 Heads would they be better ? Is the STI Heads any different to the WRX heads ?? Cams will be updated so its just the casting I need to know about ????

Thanks again for the help Lads and Lasses....

[MainFrame]

They are different.. to use AVCS heads you would need the wiring harness and ECU that goes with the later model heads.



Aside from the massive cost and hastle involved with trying to get later model 2.5L heads to work correctly on your car, the ej205 heads you already have flow more and are therefore capable of producing more power than 2.5L heads.


The combustion chambers are also different. Like you mentioned, you can deal with the increase in compression ratio by going with a lower compression piston (or thicker head gasket).. but the best way to deal with it is to have the combustion chamber machined out a little to closer match the 2.5L combustion chamber. Going the piston route does correct the compression ratio, but it does nothing for the steep step in the combustion chamber itself which is thought to cause hot spots and detonation in the cylinder. If you want the best performance you can get out of it you're going to need to rework the combustion chamber to some degree.

[Mikie13]

They are different. You'd need a different ECU/harness etc. due to the AVCS that the STI has over the 2.0L WRX heads.

Traditionally, the easiest, cheapest, and actually one of the more beneficial things to do is to just reuse the 2.0L heads and have them machined to match the 2.5L block making a hybrid longblock. They tend to flow better, and you won't have to deal with ECU and all that jazz which is a pain.

[gtrclive]

So a set of 2011 WRX heads don't flow as good as my 2002 WRX heads.... WOW thats a newsflash can anyone recommend a place to do the machining ? or are they hand blended ??

[MainFrame]

You can have them CnC'd to match, or it can be done by hand. They don't exactly have to "match" the 2.5L combustion chamber, but the edges need to come off.


Equilibrium Tuning has a CnC program service for this exact thing, they've probably done more than anyone else in the country. But there are plenty of other shops that can do the work just fine.. Head Games is a shop that does top notch head work, some of the best porting around.

Really, any good shop that does high performance Subaru engine builds will either be able to do the work in house, or they have a shop they regulary send stuff like that to to get done.

[RayfieldsWRX]

The shop that did my hybrid build sent the 2.0 heads out to be reworked, valve job, etc. It was the critical path (longest lead time, held everything else up) of the build. I've been pleased with the results, even though I went for a pretty conservative tune.