Hopefully someone can shed some light on this... As mentioned in some of my previous posts I'm rebuilding my 2.5 Hawk engine after a repeat head gaskets failure. There are a number of suspicious things that I believe led to the failure, but namely the fact the head studs fitted were rated at a lower or same power level to what I was running (roughly). I'm also considering that the RCM head gaskets that were fitted were the wrong shape for my MY of head.

It seems that between 2005-2008 Subaru made some changes to the shape of the coolant flow channels on the head. It's been mentioned in another ongoing thread that the gaskets of the wrong shape for the channels can cause issues with cooling, and I was considering this and would tend to agree, after all the engineers at Subaru must have had a good reason to make the change.

Below are the three types of 2.5 head that I can find.

2005: 4 main rectangular holes and gaskets match around top and bottom of the bore
My car: heart shaped apertures, but 3 bottom holes and gaskets fitted by the engine builder were RCM but 2005 shape
2008: introduced the heart shaped aperture and split the 2 bottom apertures into 4, and gasket matches

I'm struggling to find gaskets that match the apertures on my heads, even the Subaru stock part doesn't seem to match!

 

Your car had the wrong gaskets for the heads, should have the 06 onwards gaskets, which are the same for the 08 Hatch onwards engines.

 

Thanks for the reply, for sure I'll be rebuilding with 08MY onwards parts then!

 

as Paul mentions basically all of the Hawk 2.5 onwards use the same as the Hatch STi gasket type

all options carried in stock