Hoverjetb Posted June 12, 2020 Share Posted June 12, 2020 Hello, I am in the middle of rebuilding my EJ 257 and I have come to the step of installing the Piston Rings and Pistons. I have a sheet of paper that came with the Manley Pistons I bought that has a specific gap measurement (Bore x 0.006 in) but that conflicts with the Ring gaps specified in the maintenance manual. I didn't see any previous Forum Post on this subject so I thought I would see if anyone has prior experience/knowledge and might be able to shed some light on this. Thanks! Link to comment Share on other sites More sharing options...
Chocoholic005 Posted June 12, 2020 Share Posted June 12, 2020 I would trust what the piston manufacturer says, assuming they are pistons made specifically for your application. OEM piston ring clearances are made specifically for the stock pistons in stock boost conditions; too much boost and the rings can squeeze together and crack the piston ringland. Aftermarket pistons are obviously made for increased performance, they keep in mind that you're running more boost and are stronger than stock. All of this can effect piston ring gap. On top of it all, forged pistons have different thermal expansion than cast pistons and can change things too. Call the piston manufacturer if you're really concern and let them know the boost targets you're planning to run. They can properly advise you. Link to comment Share on other sites More sharing options...
Hoverjetb Posted June 13, 2020 Author Share Posted June 13, 2020 I would trust what the piston manufacturer says, assuming they are pistons made specifically for your application. OEM piston ring clearances are made specifically for the stock pistons in stock boost conditions; too much boost and the rings can squeeze together and crack the piston ringland. Aftermarket pistons are obviously made for increased performance, they keep in mind that you're running more boost and are stronger than stock. All of this can effect piston ring gap. On top of it all, forged pistons have different thermal expansion than cast pistons and can change things too. Call the piston manufacturer if you're really concern and let them know the boost targets you're planning to run. They can properly advise you. Thanks! I pretty much came to that conclusion myself. I appreciate your time and response! Have a good one! Link to comment Share on other sites More sharing options...
boxkita Posted June 13, 2020 Share Posted June 13, 2020 manley pistons & rings? http://www.manleyperformance.com/dl/tech/Subaru-Piston-and-Ring-Installation.pdf Build my car Boxkita Track days Link to comment Share on other sites More sharing options...
Max Capacity Posted June 13, 2020 Share Posted June 13, 2020 May be of the other older members may recall a discussion from years back about opening up the OEM gap also. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
Hoverjetb Posted June 13, 2020 Author Share Posted June 13, 2020 manley pistons & rings? http://www.manleyperformance.com/dl/tech/Subaru-Piston-and-Ring-Installation.pdf Yep that's the exact page that came in the box. Link to comment Share on other sites More sharing options...
Hoverjetb Posted June 13, 2020 Author Share Posted June 13, 2020 May be of the other older members may recall a discussion from years back about opening up the OEM gap also. It makes sense, considering the higher temps and pressures. Link to comment Share on other sites More sharing options...
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