Yup, another tire question? - same old... same old..

80 psi requires metal valve stems, so you should check what you have.

EDIT: Jim is of course correct that some of the high pressure stem are snap in type. I didn't word my initial reply very complete.

Here's a good description of the typical types of valve stems:

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=208