Phanthom

I have a 1970 Cutlass SX455 and the Fan has chewed up the bottom of the shroud. Any suggestions as to possible causes?

Olds64

Are the shroud and fan secure? If you had a failed clutch that wobbled enough for the fan to contact the shroud you'd hear it and the car would overheat.

joe_padavano

Old mushed motor mounts can cause the front of the engine to droop.
A bent or distorted frame (frequently caused by jacking up in the wrong place) can raise the trans, again lowering the front of the engine.
An improperly attached shroud or bent tabs for the shroud or bent lower bar on the core support can raise the bottom of the shroud.
An improperly installed core support, incorrect core support rubber mounts (if they've been replaced), or bent frame horns (from an accident) can also change shroud location.

Fun71

The easiest thing to check is the spacers between the top of the shroud and the radiator top plate. If the spacers are missing, the lower portion of the fan opening can be pulled up too high.

4speed455

I had an aftermarket Energy Suspension poly transmission mount that was holding the transmission up too high forcing the engine down which caused the same issue. Switched to a rubber mount and it fixed it.