[onewhippedpuppy]

The V8 is an excellent engine, with 2 issues: timing chain tensioners and Nikasil.

Nikasil info: http://www.jag-lovers.org/cjw/#0504x
Timing chain info: http://www.jag-lovers.org/cjw/#0104a

If Nikasil has not affected the engine (i.e. good compression) it won't. Nikasil problems were caused by high sulfur content in our gas, which was worse in certain states and low-test gas. These sulfur levels were reduced to safe levels by legislation in 2000, which means that 2000 and later Nikasil engines should be fine, and a Nikasil today won't degrade with modern gas. BMW had the same issues with the M60 V8. The XJR makes this my second Nikasil engine, no worries.

The timing chain tensioner is simply a design flaw that can cause them to fail and collapse. If that happens the chain can jump, pistons kiss valves, etc. There's an updated design that removes any worry that was incorporated in 2002 (I think), the updated parts can be installed on any of the older V8s. Depending on what you replace "while you're in there" the parts are around $500. My XJR previous owner had the update along with some other PM done at a shop for about $4k.