Was the engine assembled with the oil slinger on the front of the crankshaft? If it's not there and you're running a mechanical fuel pump the noise may be coming from the fuel pump eccentric burning up. The slinger is especially needed on a small block to keep oil thrown onto the eccentric and pump arm. Remember, you have steel rubbing against steel under spring pressure and it's pumping a non- compressible liquid (gas). It needs a constant supply of oil to lubricate and also cool the parts.