Royce, Although not on the list of recomemded bearing compatibily, I have been using hard Aluminum slide valves on Brass 360 for many years with out problems. 6061-T6 and 2024-T4 both work well. I "lap" both parts on a flat surface with 600 grit sandpaper and oil. Then clean very well and then clean again. Small scratches do eventually show up, but nothing that affects running. I have done several thousand cylinders that way for 35 psi saturated steam with no problems in that area. Other things wearing out yes, but no valve problems. These are 1/2inch bore cylinders.
I have made a few engines with a cast iron port face about .03 inch thick and inserted between the chest and brass cylinder like a gasket with some Loctite gasket eliminator between the new and old port faces . Then run a cast iron valve against that. That almost insures success. If that moves the valve spindle too much you might be able to mill off enough of the existing port face to bring it back to where is was. This false port face used to be used on models quite a bit, but I have not seen it used for some time. Gail in NM
