Blown headgasket... Bulletproofed?

[MPsubiesoon]

Alright so my daily, a 2003 n/a Forester has a blown headgasket. Im curious as to if I can make sure it doesnt happen again. Ive done some research and I cant seem to find the thickness of the factory gasket. My question is that 1. Can I substitue an assumingly thicker gasket (eg cosworth .78 mm or 1.01mm other assorted brands)? Will this mess with my compression too much, if at all? If so can it be tuned to correct the inbalance? I would like to see if it possibly be worth paying 4x the price of a factory gasket.

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[Bluefoton]

I've spend an anal amount of time trying so see what's available when changing mine on my old 2003 OBS. On the SOHC EJ251, subsequent revisions of head gaskets did NOT improve squat - they're all identically looking, single-layer steel with black coating on each side. What is being sold now is the 11044AA633, which superceeded the old 11044AA632 or 11044AA521 part numbers.

Now, what I would recommend - and what I got installed - is the 11044AA642. It is the stock Subaru 04-06 sti EJ255 gasket, which just happends to perfectly match the EJ251 engine as well. Multilayrered steel, and thus allegedly far more solid than our original one. The crushed thickness is a notch smaller (0.56mm vs 0.65mm), which bumps your compression ratio from 10:0 to 10:1. (+1hp as a result).

As far as preemptive maintenance goes, the word is that inapropriate coolant pH contributes to the deterioration of the gaskets, so i've been advised to closely monitor the coolant and flush it whenever necessary. Subaru recommends a coolant additive... but it's being cursed by some mechanics, since it's a rebranded Radweld which only clogs whatever hole it finds.

My 2 cents..

[cal_look_zero]

As "bulletproof" as you could hope to get, would be the above mentioned MLS gaskets, ARP head studs, Subaru coolant conditioner, and never ever driving the car, ever.

[nepbug]

Originally Posted by Bluefoton

I've spend an anal amount of time trying so see what's available when changing mine on my old 2003 OBS. On the SOHC EJ251, subsequent revisions of head gaskets did NOT improve squat - they're all identically looking, single-layer steel with black coating on each side. What is being sold now is the 11044AA633, which superceeded the old 11044AA632 or 11044AA521 part numbers.

Now, what I would recommend - and what I got installed - is the 11044AA642. It is the stock Subaru 04-06 sti EJ255 gasket, which just happends to perfectly match the EJ251 engine as well. Multilayrered steel, and thus allegedly far more solid than our original one. The crushed thickness is a notch smaller (0.56mm vs 0.65mm), which bumps your compression ratio from 10:0 to 10:1. (+1hp as a result).

As far as preemptive maintenance goes, the word is that inapropriate coolant pH contributes to the deterioration of the gaskets, so i've been advised to closely monitor the coolant and flush it whenever necessary. Subaru recommends a coolant additive... but it's being cursed by some mechanics, since it's a rebranded Radweld which only clogs whatever hole it finds.

My 2 cents..

I too have been doing a ridiculous amount of research into the head gaskets for my 02 OBS. I also settled on the 11044AA642 STi head gaskets. I would say any MLS gasket will be a good improvement.

I've still got a little while before I tackle the job (no leaks right now, this is preventative stuff while I have the engine out), so now I am researching whether I want to use a Copper spray, Hylomar spray or put nothing on the gaskets when I do it. I'm currently leaning towards Hylomar.

[cal_look_zero]

Originally Posted by nepbug

I too have been doing a ridiculous amount of research into the head gaskets for my 02 OBS. I also settled on the 11044AA642 STi head gaskets. I would say any MLS gasket will be a good improvement.

I've still got a little while before I tackle the job (no leaks right now, this is preventative stuff while I have the engine out), so now I am researching whether I want to use a Copper spray, Hylomar spray or put nothing on the gaskets when I do it. I'm currently leaning towards Hylomar.

Nothing. The LAST thing you want, is the potential for any surface irregularities to be on those gaskets. Spraying something on there totally unmetered is a big no no.

[oem]

I am surprised no one is talking about Cosworth FLS head gaskets. I am not a fan of their current engine program but their head gaskets are top notch.

Here is a good tech article where Cosworth pressure film tested multiple gaskets.

http://www.motoiq.com/magazine_artic...-released.aspx

Also multiple thicknesses are available to maintain proper deck height after machining the head or block.

[pilfflip]

The infamous gasket failure of the OBDII 2.5's was taken care of in the earlier OEM gasket designs. Any OEM gaskets meant for your Forester engine will be fine now. OEM is never a bad way to go and there's no reason to get anything extra unless, that is, you're looking for reason to step up to a higher performance gasket. Make damn sure that you're getting the right gasket, though.

[boilermaker29]

I would spend less time worrying about the gasket type and focus more on the procedure. As long as you're using the updated gasket you've greatly reduced your risk. The problem is when people dont properly prepare the mating surfaces. Which IMHO requires pulling the engine. You can use a super duper gasket and it will still fail if the surfaces arent straight, cleaned, and at the proper roughness.

[pilfflip]

Agreed, there's also a very specific torque down procedure for the heads. It usually take 15min or more if done properly.

[MPsubiesoon]

Well id like to thank everyone for their input, but my problem got solved. My fozzie is/was totalled

[Bluefoton]

Sorry to hear about it... but a peeled off bumper and some dings on the hatch equals totalled ?!

[walhalla]

I am an auto body tech and do lots of insurance estimates. It does not take much to write a car off.