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Old 06-27-2003, 01:44 PM   #1
Scooby Newbie
Member#: 7038
Join Date: May 2001
Location: Canada
1998 2.5RS

Default Yet another head gasket question...


I've yanked off the heads to my 98 RS, and I'm going to replace the stock head gaskets with the new 4-layer head gasket from Subaru. I was also going to O-ring the heads, but the guys at the machine shop said it's not necessary for low boost applications (0 - 10 psi), especially since I'm going with the new head gasket. He also wondered if this 4-layer head gasket is compatible with O-ringing (which I have no answer). So, here are the questions I need some answers:

1. Can I safely change to the 4-layer head gaskets, and not O-ring (again only running less than 10 psi)?
2. Is the 4-layer head gasket O-ring compatible?
3. Has anybody blown the 4-layer head gasket, and what boost pressure did it blow at?

All help is appreciated!


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Old 06-27-2003, 05:42 PM   #2
Scooby Specialist
Member#: 5786
Join Date: Apr 2001
Location: RS202

bump for the damn good question
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Old 06-27-2003, 05:52 PM   #3
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Join Date: Mar 2003
Location: San Diego
04 04 STI
No AWD, Not interested


I'd even sneak this over to Cobb since they're working on a kit.
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Old 06-27-2003, 10:38 PM   #4
Unsung Boxer
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Join Date: May 2003
Location: WA state

Oh wow, dont listen to the machine shop guy. Prime example on this board: Darshu, blew his 98 RS head gasket @ 4 PSI.

The problem is that Subaru NA head gaskets are natorious for blowing and not staying in, even when NOT underboost. It has become such a problem that subaru has had to redesign their head gasket to the new 4 layer one, however, this does not necessarily make it better for boost. If you have the heads off, spend the money on the o-ring job, because it will save you time and money in the long run. Also, you wont have to worry about the head gasket being the weakest link.

BTW... they are compatible. If Im not mistaken, the new head gasket has metal rings in it that confuses people because it looks like it itself is an o-ring. No, this is just part of Subaru's new design. The o-ring actually goes outside of the perimiter of that metal piece to provide an extra pinch.

Here is a pic

This cost me 80 dollars, Darshu paid 140 for his job... depends totally on the machinist. BTW, some peope use Copper wire, other's use mechanice wire. I used mechanics wire because it is less likely to get marred when putting it in, like copper.
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Old 06-28-2003, 08:20 AM   #5
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Join Date: Aug 2000
Chapter/Region: NESIC
Location: Raymond, NH USA
1995 Impreza w/EJ255
Brilliant Red

Default O-Ring

What are people's thoughts? O-Ring the block and the heads? Just the block if the engine is out? Just the heads? Is there a head gasket for the MY98 that will lower the compression some?
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Old 06-28-2003, 06:54 PM   #6
Unsung Boxer
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Join Date: May 2003
Location: WA state

you can do it 2 ways:

1. Lay a groove in the head and put the Wire in that groove, of which some of that wire sticks out and presses the gasket to the block.

2. You can put the groove and wire on the block, and a "reciever" groove on the heads. This pinches the gasket between the wire and the reciever groove.

The first method will solve the problem, the second is even extra insurance.

the other problems that arise doing this is that the block is way heavy so you will not only be transporting the heads, but the block as well. This is much more expensive because you have double the machine work to be done, plus the math to line up the reciever groove w/ the wire. And most machine shops wont work on parts that are perfectly clean, most require a chemical bath which is expensive and damaging to gaskets.

This is why I personally chose method 1. It worked for many including Darshu, i am confident it will work for me.

Hope that helps
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Old 06-28-2003, 08:00 PM   #7
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Join Date: Jun 2002
Chapter/Region: MWSOC
Location: Ishpeming, MI
1998 Red Wagon
New Turbo Project...

Default Jake...

I concure with Jake on this one. Do it right the first time. Even though you say you're only going to run under 10psi, you never know when you might want to turn it up a notch, or the boost could spike. Its cheap insurance and doesn't hurt anything.

Jake - One question I have been meaning to ask is if you placed the seam of your wire adjacent to a head-bolt? I noticed in the picture its not. Since thats obviously the weak-point in the o-ring, it's suggested to place it as close to a head bolt as possible for the strongest clamp. I'm sure it's better than no o-ring regardless.

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Old 06-29-2003, 02:40 PM   #8
Unsung Boxer
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Join Date: May 2003
Location: WA state

I had the machinist do it based on wayne's description.

THeoretically there should be even pressure by the head onto the block if torqued properly, thus the oring should seat no matter how close are far from the stud.

At any rate, im sure its fine, im really not worried about it.

BTW, hurry up on those pipes
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