I have several 2.4" OD cored. Will overheating cause their properties to change after they cool down I have 2 out of an AV640 that now have a dull surface. I have quite a few new ones, so replacing them is not a problem, but at near $5 each I'd like to save them if they are any good. The material is nor cracked/fractured. 73 Roger (K8RI)