As I understand them, you can
As I understand them, you can replace the valve core, but not the stem. If the threads on the outside of the stem don't allow you to screw the cap on, you might need to run a die over the threads to clean them, or use a plastic cap rather than the original metal one. I doubt the internal female thread on the stem could be damaged. Usually, remove old core, clean, insert new core. Getting dust, dirt, filings or other debris inside the chamber could be a problem, There isn't enough air volume to puff them out and they could jamb the valve and give you all sorts of grief. So avoid chasing the internal female stem threads with a tap.