I can manage about 4.6 I can push it to 5 but it gets scary hot.
overclocking is pretty machine specific, the best thing to do, if you insist on doing it, is increase by small intervals and use an app to monitor the temperatures and make sure you're in safe ranges under load.
You can just google the chip and overclocking and you'll soon discover that there are about 30 ways to get there and they all work with varying success for different people and setups.
The best way to overclock is to honestly do it yourself.
Learn the frequencies know what the numbers all mean, it's the only way you'll ever get the most out of it.