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If water is coming through it then it must be pressurised so would need welding surely, does the piston skirt come down that fair, if yes would the rings come down that far, if yes for either why not drill the hole a bit bigger, tap a thread and put a small bolt with loctite in there then carefully file the head off the bolt.
Or even a tek screw, saves trying to tap a thread.
Ginger
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