I agree dcdoug, the motor needs to be thoroughly looked at, just suggesting ways to asses if any serious damage visible. Since you stated they are pliable, not hard and brittle, they may be bits of some sort of gasket sealer the builder used rather than metal bits. I've always built my own motors, and having a few bits of sealer in the
oil pan later isn't unheard of, no matter how careful you are during assembly. I tape magnets on the
oil filter to try to contain the fine particles from breaking in and wear. Bigger chunks of metallic bits in the
oil pan are never good, they came from some component somewhere.