No, Dont do any filing of the sides of the rings--Best left well alone. Only Ever file the end-gap if the clearance when checked is tight, and make sure its done Carefully and perfectly 'square' to the ring ends.....

Great care must be taken, Rings are very brittle and can Easily break.

If you file the sides, it will affect the sealing and they may never bed in properly....

The maker will have given them a tiny radius of around 1 degree on the face to ensure they bed prooerly.

Yes, SP.030 sound about right, for a 91mm bore This is the clearance value. Its the Piston Size, Plus this 0.30mm which they bore the block to....

Worth checking the Block has a chamfer at its top of 45 degrees, and around 1mm to allow ease of ring install. A sharp edge to the top of the bore can catch and break the thin edge off an oil ring....

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Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....