[Pete]

First try easy stuff like belt tensioner then try the 1500-2000 rpm for about 30-45 seconds if sounds starts to quiet down your on the right path.

If it's chain tensioner issue it should not hurt anything the worry is if a chain guide is bad/broke now you have metal to matel.

When the LT5 sits for a while lifters do/could bleed down.

Try above let us know outcome.

Pete