One of my head gaskets has recently given up the ghost on my 2005 WRX (EJ205 - no mods) engine. So I've got the thing apart now to start fixing it.
Looking at the heads and measuring their sizes it appears they have been skimmed in the past and the old head gaskets are over 1mm in thickness, and they appear to be MLS type.
Given that the head have already been skimmed (reckon 1mm taken off?), I'm assuming getting another similar skim wouldn't be possible. I don't think the heads have warped, but haven't really checked properly. However the surfaces aren't the cleanest (it appears some sealant has been used) so would I need to resurface them?

Also, what replacement head gaskets should I use? Obviously will need thicker ones, but shall I go for RCM, standard Subaru, or Fuji Racing ones? Does the choice of gasket determine how the heads should be resurfaced?

 

When you say you have measured them, do you mean you have CC'ed the Combustion chambers? What volume did you get?

OEM with no material removed should be 49- 50CC for a UK Car what you have left (assuming OEM spec, 92mm pistons) gives you what you can remove safely.

You origianally would have had 0.78mm Gasket in there so if they were skimmed 15 thou then I would think a 1.1mm Gasket is in there now. head must have been in a very bad state to have 1mm machined off it.

Biggest you can get is the old 1.6mm MLS ones (originally from the V3 and V4 STi's) so there is still room available?

Other option is speak to the likes of Matty Baker at MB Developments and get an unubused set of Newage WRX heads that have never been skimmed and go from there?

 

Unfortunately, big end bearing failure usually follows head gasket failure fairly quickly with Subarus, as in like 500miles, so whilst it's apart you're best off doing a full refresh.
Or for easiness just buy a new short block and bold your heads on.

 

No, I haven't really got the bits to measure the cc of the combustion chamber at the moment. So I just measured the height of the head, and it was about 126.7mm (IIRC), so less than the original 127.5mm quoted in the specs. Probably not the most accurate way of checking. I might have a go at measuring the volume of the chambers if I can get hold of some bit to do it.

 

Is this big-end failure due to a particular type of head gasket failure? Mine appears to be a coolant to chamber failure rather than coolant to oil one. My oil was clean when I drained it.

I'm running out of space in my garage for spreading out part at the moment, not helped by other car's engine deciding to let go today!

 

a head casting should require a "few thou" skimmed from it at most, nonsense if people are skimming 1mm+ from them.............

in our experience the RCM ones are the 'best' and have poor experience with other brands (other than Cosworth who tend to be slightly more expensive)