Depends on your definition of "a lot of clatter" :-(
I would do the following: without turning the car on.
In no particular order:
check your oil level is it full (or at least not low)
check your coolant -- any intermix?
check codes with a duramatic -- even if no CEL.
pull the plugs and boroscope the cylinders, check compression
check the timing.
see if you can boroscope the chain tensioner paddle
and check to see the chains are in good order.
pull the oil filter and check for metal flakes.
pull the oil pan housing and look for metal and other debris.
sadly -- there is no way to inspect the IMS without really getting into things.
where are you in Texas -- I work with a mechanic in Austin
that rebuilds M96 engines.
Love to help you if we can. For a faster response -- send me an email,
I don't always see the PMs.
Mike
mike@lonestarrpm.com