Pot metal was not only an automotive problem. Any mechanical items that were mass-produced from the mid-1920s to the early 1930s contained pot metal and failure is expected. I run across it radios, clocks, piano actions, statuary, phonographs (especially reproducers), electrical switches and knobs, and elbows and nipples for vacuum lines. Swelling and cracking are obvious but often while looking good it will disintegrate with any usage.
When I was young ( in my mid-60s now) the oldtimers always said the fresh batch of metal they made on Monday made a good product but by the end of the week after constantly being reheated with the sprues and leftover metal being tossed in, you were lucky to get a year.
I hate the stuff but it seems to be part of all my restoration projects.