66 T-Bird Loses Oil Pressure

When I first start T-Bird, oil pressure on guage is on or above halfway, however; after running approximately 30 minutes pressure goes to Zero, no clicking of lifters are heard. What can this problem be?

Install a good quality aftermarket oil guage such as a SW or Autometer to acurately check the pressure. Are you using a good quality oil and filter? Since you don't hear any lifters clacking the oil pressure must be more then zero but probably pretty low. Change the oil and filter and check it again with the new guage.If it still drops way down then it sounds like it's time for bearings and new oil pump at least.