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Discussion Starter #1
After spending all morning reading up on head gaskets and head gasket failures I was wondering a few things. First let me give some background:

MY00 2.5 RS-T. I blew up the stock pistons. I replaced the rods and pistons with forged low compression (8.5:1) replacements. I later found out that the replacement pistons were designed defectively, and needed to be replaced. This past weekend the new pistons went in the motor. Upon inspecting everything it appears the prior set of aftermarket pistons were slightly making contact with the heads, as there were marks on the piston tops and the heads. The valves were fine. In looking at the new pistons, when they are at TDC they are not flush with the block. They actually stick out past the end of the block a small amount (haven't measured it yet). We noticed this after taking all of the pistons out, so I don't know if these stick out further or not than the set I took out.

I would assume that the pistons hitting the heads, would explain a lot of the noise I was getting that everyone was attributing to common "noisy forged pistons".

In reading I have found several references to "stacking" head gaskets, i.e. using two 99+ head gaskets on each side.

My questions are:

Has anyone here actually used multiple head gaskets on each side? What is the expected durability of such a setup?

Do the stock pistons (or anyone who has aftermarket pistons) fit flush with the block or extend past the end of the block a hair? I haven't seen a stock block to compare this to.

I would like to prevent the pistons from hitting the heads, for obvious reasons. So I trying to gather more information.

Thanks,
 

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Wht you need to do is find out the compressed height of the head gaskets, then mike (use a micrometer) how far the new pistons travel above the deck. if they travel above the deck but not higher above than what the compressed height of the headgasket is you are fine. That's weird though. I only hear of people doing that for extreme race motors. Usually people want the piston to be about .010 under the deckheight. Make sure and check that out. I wouldn;t suggest stacking head gaskets.

Looks like you might need a new set of pistons or rods. Did you measure the rods centerline to centerline before putting them in to make sure they were exactly the same length? Good luck

Eric
 

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In all my years as a mechanic I've never seen a street engine with pistons that come above the deck hieght. I think you probably have the wrong lenght rods or improperly machined pistons. If anything, I would expect low compression pistons to be lower than stock. I would not suggest stacking the gaskets, as the gasket surface is designed to have some "bite" on the machined surface of the head and block, and stacked gaskets would probably tend to leak where they meet. Maybe not right away, but after a few thousand miles anyway.
 

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2000 Subaru Impreza W"RS"X BRP
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I would...

How can low compression pistons reach higher than the stock slugs? Makes no sense...They sent you the wrong pistons or you are using a longer rod...Somethings not right...Don't assemble the engine...Remove the rods and pistons and take some measurements...Compare the numbers to the stock parts and take your results to the dealer you got your gear from...

Zee:checkit:
 

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The MY99 pistons with the square relief ARE taller than the MY00 pistons with the cut valve reliefs. We noticed this on 8Complex's car when he had the engine apart. The older pistons came slightly above the level of his deck, so he couldn't use them in his MY00.

Your pistons may possibly be designed for the DOHC head as well....
 

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everyone FYI porter is the MAN!! even if he forgot who i was ;)...hehe j/k porter
 

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Discussion Starter #9
I am going to try a thicker copper head gasket to compensate for the amount the pistons stick out of the block. They stick out about .025" so the head gasket just needs to be about twice as thick as stock to allow the proper clearance.

I realize that this is not the correct way to deal with it, but after 7 months of fighting with the vendor to get this far, I am not willing to wait for several more months for the vendor to try and help me.

I should have the gaskets by the weekend and the motor back in the car. I will let people know how this works, as I have found out I am not the only one with this problem...

Thanks for the suggestions everyone.

Aaron
 

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good luck aaron...also w/ the copper head gasket you may need to retorqe it after a lil bit...read the directions VERY throughly.
 

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forget head gaskets... i was just watching tv and they had this stuff you could spray on leaks to seal it up. they took a knife and cut a garden hose then sprayed it and voila (sp?) it was back to normal! just use that stuff. :lol:

that stuff should seal everything up hahah
 

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Andrew said:
forget head gaskets... i was just watching tv and they had this stuff you could spray on leaks to seal it up. they took a knife and cut a garden hose then sprayed it and voila (sp?) it was back to normal! just use that stuff. :lol:

that stuff should seal everything up hahah
LMFAO!!!! haha well in that case would you interested in some land in florida?? hehe
 

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man when i retire.... im moving to FL. im gonna be the only old guy with a fast car. im gonan piss some retired old peoples butts off. im gonna start talking to some old lady and talk quietly then tell her to turn up her hearing aid...when she does this im letting the BOV go off! PSHHH!!! AHHH!!! hahahaha....im gonna tan in my boxers and undershirt in my lawn and drive property value down. then im gonna buy everyone's houses and turn them into garages for my cars. when a house gets messy i move to the next one. after about 5 houses ill call the maid services and tell them to start cleaning the houses.


sorry, im just whoring.


i wonder if FL calls grapefruit shooters orange shooters? :confused:
 
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