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Old 07-26-2006, 11:25 AM   #1
Scooby Rex
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Member#: 114920
Join Date: May 2006
Chapter/Region: TXIC
Location: Plano, TX
Vehicle:
2003 WRX Sedan
Silver

Default ej20 arias .020 over pistons ring gap

I am just about ready to send my short block out to get it bored for my .020 over arias pistons. When it comes back what should I gap my rings at? I can't seem to find this info.

Also, the standard head gasket is 93mm. Will I need a different head gasket for this new bore size? If I do, do you know where I can get the different size gasket and exactly what size I would need?

As you may be able to tell... I have never rebuilt or changed out the internals of an engine before. This is my first time so I appreciate any info/help that can be provided. Thanks,

Scooby Rex
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Old 07-26-2006, 01:47 PM   #2
bboy
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Member#: 56468
Join Date: Mar 2004
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Location: Seattle, WA
Vehicle:
04 Improved STI
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Ballpark numbers:

Conservative: 0.0055 X bore
Aggressive: 0.005 X bore
Risky: 0.0045 X bore

I'm assuming max 20 psi of boost from something bigger than a stock turbo and this is a primarily street-driven vehicle. More boost means more heat and more expansion especially of the top ring.

There are debates about if the second ring should have a smaller gap or not.

You will not need a new headgasket for that overbore. There's a thread in this forum that I started that will give you the exact dimensions of the stock 2L head gasket.
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Old 07-26-2006, 11:10 PM   #3
conoval21
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I would recommend .0055 for every inch of bore. If your rings touch, you will wish you had that extra few thousandths. Many agree that it is best to gap the second ring about .002" larger than the top ring. The idea is that you do not want the gas pressures to equalize and lift the top ring.
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Old 07-27-2006, 01:04 PM   #4
02Toyowrx
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Arias pistons are not setup to use factory type rings.
Your ring gaps should be as following for a street/race application. If you are also using nitrous, and or plan to put alot of boost (30+psi I would increse the gap a little)
Top Ring- .017" - .019"
Second Ring-.019" - .021"

Make sure you keep consistant gaps on the rings between each cylinder.
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Old 07-27-2006, 02:32 PM   #5
SubyDuz
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69 IchhateinAudi
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ARIAS pistons are horrible...I have had two motors assembled with Arias pistons and both times the motors failed. cause was the pistons, once they went egg shaped...I highly highly caution against arias pistons. This was just my experiance...so take it as it is

Motor now has CP pistons and hasn't had a hick up, nothing else changed by the way....nothing
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Old 07-30-2006, 11:24 PM   #6
bboy
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Well that is a vote against Arais. Read the piston FAQ. CP and Mahle have gone into quite a few cars. CP makes the pistons for a few of the big engine builders.
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