<VV> Case Hardened Lifters

[Brian]

I recently acquired a set of Isky lifters for Corvairs.  The box has an old Clark's number sticker.  Printed on the box is a warning stating that these lifters are for use only with case hardened cams.  The box also says that th elifters are case hardened and the contact face has a light black color.So, my questions are--aren't all cams hardened?  Are there any cams that I can't use with these lifters?
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