Engine rattles when cold

[rdodd]

I had timing advanced to about 14*btdc over the summer and engine noise is less and i have better throttle response, but now since the mornings are getting colder i notice a real loud intermittant rattle under light load for a few minutes until cold start valve shuts off. Before the timing advance the noise when cold under light load was only slightly louder. Could timing be too far advanced or is it normal to have this real hard rattle when cold?