First, take it apart as littel as possible. Obvious and totally unrealistic during a huge build
Second, when replacing the valve in the tube (and this is true of the 13xx/22xx/39x platforms too) take great care to get the hole on the valve to align as close as possible with the hole in the tube.
======>> Do not use the screw to align the valve and tube, do not use a metal rod (drill bit, small screw, one jaw from needle nose pliers, and others Ive used but cant recall) to align the holes during reassembly. If you must tweak alignment, use a small wooden dowel..... I learned this the hard way on my AC397 build. Totally trashed a valve half
Bear in mind the aluminum is fairly soft, and will distort and fail under pressure from steel tools......
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