The Stovebolt Site Forums The Shop Area Engine Shop Straightening the Rochester B and BC castings

I suspect the metal to be a zinc-aluminum alloy ("Zamak" is an example).
Yes, it's heavy, but the zinc adds a useful characteristic: it holds fine casting details and threads better than aluminum.
400° F is safe because it melts above 700°; this saves energy in manufacture ($$) compared to aluminum which melts above 1200° F.
It can be soldered.