2T loud rattle/clunking at 800RPM

[merc-blue]

After driving my TA22 to dandy and back (sits on about 4Krpm at 100kph)
It has developed a rattlley clunky sounds adt 800-900 RPM and not above,
I has had oil and water and was running almost spot on 90 degrees like a champ,
Any suggestions? im guessing somthing valve train possiply totaled a timing chain guide? or loose crank pulley but they are totaly blind guesses, any suggestions to look at?

[Hurricane]

just check over the engine bay, maybe some loose tin wear or something? how loud is it?

[merc-blue]

REALLY LOUD,
but its all fixed, altinator was loose