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Old 01-18-2021, 09:08 AM
lr172 lr172 is offline
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,856

Originally Posted by avrojockey View Post
About 1300 on a field overhaul that was thorough and extensively documented. almost 700 since topped with new ECI jugs....engine is running very good with clean oil so I would hate to jump to any conclusions.

Wouldn't fretting show up in oil analysis? Screen and filter have been clean, and AL is 5 ppm which is the universal average. Also, wouldn't fretting cause seeping at case split? I don't think anything is coming from there...either on top or bottom. Or, is it fretting between the through bolt and case?
The case fretting does not produce a lot of metal and I doubt it would show up. The only exposure that the studs have to oil is where the case halves come together at the split line. I think that some older cases didn't have orings, but shops would machine a channel for orings in that spot to elimnate oil migration when the case was in for re-work. I believe it is common for wear here and oversize through studs are used. My 540 had 4000 hours and Divco had to put in all new studs when the case was overhauled to met the clearance spec.

Was your case sent in during the overhaul? If so, they typically machine down the case to address the fretting. If orings are not used on the through studs, case fretting would allow oil to migrate into the stud clearance area, if present, and work out the case end. This is getting to an area where you need some expertise to determine how concerned you should be.

N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019

Last edited by lr172 : 01-18-2021 at 09:11 AM.
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