500SL upper engine ticking noise.
 

Hey guys. My dad let his 500SL sit for a good while and when he fired it up and decided to drive it again it started making an obnoxiously loud ticking and it sounds like it's right under the valve cover on the passenger side. Here's a link to a short video.

https://1drv.ms/v/s!AoDBgKAcPey1hTf1m5xWAkmJiB_M

It's a 1990 500 SL with the 5.0

Any suggestions would be great, as there aren't any decent shops where he lives.