Does anyone know if the piston is suppose to have a coating? When i took my piston out I cleaned it up with a glass bead blaster. I passed it over the whole thing lightly to get it clean. My guy putting the engine together said I shouldn't have done that as some pistons have a coating. It is within spec otherwise. Should I order a new one or do you think this one is fine. He seems to think it will be ok but he is leaving it up to me.