Subaru Forester EJ205 headgasket replacement

I am doing an headgasket replacement on my 1999 Subaru Forester, i always resurface the heads but i was wondering what people's opinion is on resurfacing the bottom end.

Kind regards,

Coy Onderdelinden

Hey Coy

I've done many headgasket jobs on subarus. I typically recommend decking the heads and replacing valve stem seals. For the bottom end, I usually clean it up myself and ensure there is no gasket residue left behind from the old headgasket. Once it's clean it's good to go. I personally have never decked a bottom end, and I've never had an issue with any headgaskets that I've replaced using this method.

Best of luck

With engines, as a general observation, skimming the block is usually un-needed unless corrosion or a leak on the block side of the gasket has damaged the surface. However, using a GOOD straight-edge to check the surface is flat is always a very good idea, especially with an alloy block engine that may have been overheated at some time.

Use of the straight-edge is also advised for checking the head, as often skimming isn't actually needed unless there is actual damage.

Measured the deck and it was within oem spec.

Did the heads, it was needed.

And i redid the valves/ground the valves because they where very leaky.

Thanks guys.

The other issue with decking Subaru engines is that you are narrowing the engine by the amount of deck work being done, and this can cause issues with the older style trigger patterned engines (not the 36-2-2-2) as it can cause one of the sync edges to swap to the other side of the crank edge and the ECU doesn't sync because of it.

While it doesn't make things perfect, these help a bit with the concern Stephen mentioned:

https://www.iagperformance.com/iag-performance-adjustable-timing-idler-kit-for-ej20-ej25-subaru-wrx-sti-lgt-fxt/

If the heads need decked far enough, I start over with new heads.

And +1 for just deck the heads not block, but check it like Gord said. If the block needs decked, you're in for a much better job and may want to consider alternatives.

Also, this is a good time to consider basic ARP head studs, and make sure the root cause of the gasket failure is found and fixed. Those engines don't blow gaskets without something being very wrong i.e. severe overheat or knock.