Hi, please advise on my '98 XJR built 02/1998.
I've had an intermittent low oil pressure warning msg off and on for some years now since an accident in 2004. I only put about 2k mile per year on the car and the problem seems to occur after long idle periods in storage. I even had the oil system flushed after an oil/filter change didn't seem to fix the problem. (I didn't believe in them either but it did the trick!) I only use Mobil 1 5w-20 in the car.

Recently, after sitting for 14 months with only intermittent startups the msg became persistent. I drove it easy, took it out on the highway, msg turned off, had no problem. But the msg returned when I slowed for city driving. A couple of days later after more occasional slow speed city driving I heard what I think is knocking on bottom end. Though it seems to quiet when revs reach 1200-1500. I'm afraid I've spun a rod bearing before I could get another oil change and check!)

BTW, the dipstick always showed levels to be full and clean, a bit on the high side but not overfilled. Oil had about 4k on it. No valve ticking on startup. No leaks, no smoke, no signs of oil consumption.

My expensive mechanic wants to change the oil strainer, and thinks the bottom end may be OK. But...just in case, he has a spare low mile '02 XJ8 engine unused from another swap.

If necessary, can I move the induction and pulleys from my engine onto the '02 4.0 XJ8 long block. Will I need to keep my heads? What are your thoughts.

 

if it has spun a bearing, it'd be much easier to replace that, than swap bits over to a non s/c engine.
The only thing of use on the n/a unit, is the block and crank, and once you remove the pistons and con rods, you may as well re-shell it.
Second opinion time I'd say, look for a good Jag indi. By the way, AJ-V8 units always use 5-30 oil don't they?