Sounds to me like a classic case of timing chain has jumped a tooth or two, a quick removal of the rocker cover & you could confirm if that's the case, & if it has jumped have a good look at the Cain guides, cos they can break & aid in the chain flapping around & that's probably the noise you can hear.. it's not a big deal so don't panic about it as you only have to drop one of the cam phases off, jump it back to where it should be & replace any broken guides ( hopefully it's only the top one ) cos it's very accessible, rocker cover back on & should be fine .. good news is the won't bend the valves on those engine's.. anyway good luck with it & let us know what you find..
DJP.
