It will not hurt anything to run it like it is. However it will hurt your performance and fuel economy because your timing will be late at speeds above an idle. If you have someone close to help you, make sure that you have a vacuum chamber available so that if it is bad you can replace it when you have the distributer out because the distributer has to be out to replace the vacuum chamber and then of course it will have to be timed after you put the distributer in. There are many old GM inliners running around with a bad vacuum chamber, and yours may have been bad for years.