RE: AME engine mod's for racing
Going back a bit and reading this thread, I realized I didnt comment on the "circular" cut on the bottom of the piston you seen. that is there so the piston on the .061 will not hit the back cover at BDC. The .049 clears so it isnt relieved there.
On my modified pistons, that "circular cut is completly machined away. If you are kinda handy with a dremel tool, it is easy to do as long as you dont go too wide with the window you are cutting and only go as deep as the counterbore in the piston.
Great fun!