I replaced my Valve cover the other day and obviously had the cam cover off to do it and noticed a quarter inch wide groove that looks like was evenly dug into the timing belt on the inside just before the inside edge. It's cut maybe an 1/8" deep into the timing belt. What would cause this and is the timing belt compromised to the point that it will need replacement?? It would really suck if it did because I can't imagine it would be cheap to fix. Here's a pic. Thoughts??