I started a thread in the XJS section to find out if the cam cover on the later years of the XJS were made out of magnesium or aluminum. Every picture I have seen of an XJS with the same engine had a perfect cam cover. But not to be. However the thread below has generated a lot of discussion regarding the ^&*@# magnesium cam covers as can be found here. X300 owners might be interested in this thread.
https://www.jaguarforums.com/forum/x...-cover-108993/