I wouldn't try going 4 Ghz with your current set up. If you are getting 46-48 degrees Celsius running 1.008V then you probably need more airflow going into the case. Also you need faster ram. In terms of temps, put it this way, I have the e8400 running at 1.25V at 3.6GHz and my idle temps are in the low 30s. What are your CPU voltages running load?
like 58 C