Found this on You Tube. since there has been a lot of discussion on valve adjustment on the V12


Hope the link works, it is interesting

 

I think some people avoid this on the XJS altogether, because getting down to the shims is more time consuming than on an XK, but then again, I have had a 5.3 apart with 100k miles and the shims were still in spec. I think most people will never need to do this on their cars, as people get rid of or avoid cars with high mileage. That being said, if you have a 5.3 with 200k on it, it will probably run a bit better with some adjustments

helpful video either way, lots of people are unfamiliar with shim type adjustment

 

That is true, but since I have been checking and checking thing under the bonnet. Wiring all checked over, new injector harness made, and doing much needed engine cleaning (figure since I decided to put up the Jag back in Oct) check over as much as possible and change some gaskets I might as well check the valve clearances, not really going to get into changing shims, hopefully, on 57000 on mine. but been yrs and yrs since I worked on a Jag, kast time was about 1973 when I was in trade school.

 

well if you check the clearance and it needs shims, you most certainly should bother changing them!

I know what you mean though, checking everything brings peace of mind.
You never know when it will change though, just yesterday my mirror came loose after 5 years of nothing and today i shifted into reverse hard (probably needs some trans fluid).
Always something going on...