Rattling noise from the front of engine

There is a noise coming from the front of the engine ( not the exhaust bank but around the accessory area). I want to know what it could possibly be. it sounds like shaking a metal can full of bearings but it only does this at idle. Also my buddy thinks i should replace the motor instead of the timing chain. any suggestions?

Supercharger coupler.

YouTube - Replacing a worn out supercharger coupler on 3.8 GM engines
Make sure you watch this.

thanks guys, looks like a relatively easy fix.