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Old 09-05-2010, 01:44 PM   #1
crswjr
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Default OEM Piston Ring Gap?

Found out that some of my OEM pistons are broken.

Replacing them again with new pistons, and new piston rings.

What is the OEM Piston Ring Gap and Positions?

Any help would be greatly appreciated.

Thank you.

Edit: More info given.

2004 STI 2.5L

60,000 KMs. Not miles.

Cylinder walls still look like they came out of the machine shop. (Very visible cross hatchings. Looks fresh)

Found the tolerances and gaps for rings.

OEM ones from the dealership are good the way they are. They don't need to be filed.
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Last edited by crswjr; 03-01-2011 at 03:14 PM. Reason: Answered. More details given.
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Old 09-10-2010, 12:28 PM   #2
sackytar
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If you found em then post em. Be opensource for the community.
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Old 09-10-2010, 11:10 PM   #3
sense of nature
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Y go w oem pistons if you already broke em?.. Just saying they are likely to break again no?
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Old 11-08-2010, 11:12 AM   #4
crswjr
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The Piston Rings are pre-gapped from the dealership. They didn't to be gapped.

As for the rings breaking-- it wasn't me who broke it. I bought a bad motor. I was burning lots of oil. Turns out it was 3 cracked pistons.

Had the pistons replaced, and the rings replaced.
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Old 11-08-2010, 11:13 AM   #5
arghx7
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how about you tell us what engine this is
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Old 11-08-2010, 11:22 AM   #6
arghx7
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'05 STi





ring gap

Top ring: .0079" - .0098" limit .039"
middle: .015" - .020" limit .039"
oil ring: .0079" - .0197" limit .059"

ring-to-groove

top ring: .0016" - .0031" limit .0059"
second ring: .0012" - .0028" limit .0059"
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Old 11-08-2010, 09:55 PM   #7
ballitch
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You did have the block looked at by a machinist didn't you? If there are grooves and ruts in your cylinder walls, it's still going to burn oil like it is now.



~Josh~
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Old 03-01-2011, 03:12 PM   #8
crswjr
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'04 STI.

60,000 KMs. Not Miles.

Cylinder walls still look like they came out of the machine shop.

The numbers that user: arghx7 provided is what's used.
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Old 03-01-2011, 06:27 PM   #9
Ryan314
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You NEED to get the block looked at by a machine shop. No exceptions.
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Old 03-01-2011, 08:45 PM   #10
2Fast4U1DAY
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Quote:
Originally Posted by Ryan314
You NEED to get the block looked at by a machine shop. No exceptions.
This^^^^
I don't care if that engine has 370 mi or 37000 mi. The rings wont seal if you don't get a light hone, and you will STILL be consuming oil. Just because you can see the factory hone doesnt mean you can just throw pistons and rings in and be good. Theres MUCH more to it than that....
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Old 03-01-2011, 09:09 PM   #11
BlackFighter
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and for god sakes don't use the stock pistons, you will be back here in no time.
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Old 03-02-2011, 02:51 PM   #12
2Fast4U1DAY
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Quote:
Originally Posted by BlackFighter
and for god sakes don't use the stock pistons, you will be back here in no time.
People dont use the most valuable tool in their arsenal nowadays. If they used their brain a little it would make sense to go forged but nothing changes if nothing changes....
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Old 04-04-2011, 01:37 PM   #13
crswjr
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Update: 10,000 Miles and counting. No oil burns. Car runs very well.

Thanks for everyone's concern, but I'm confident in the rebuild.

As stated before, it wasn't me who broke the cylinders in the first place. It's a daily driver, and I'm not an agressive driver.

Thanks again for the concern, and the help. Maybe in the future, I will do a full forged/big-turbo setup. For now, I'm very happy with what I have.
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