When starter turns crank, it sounds like a few cylinders don't have compression.
I guess I'll have to remove heads, replace a few valves.
Where to buy cheap valves, head gasket set and timing chain kit?
Which year XJ8 engine will fit my car?

 

best of luck with the repair process. You might want to consider buying the best parts you can find, not the cheapest. spend the extra $$$ for stock Jaguar valves, or some Ferrea valves, and a quality timing set. I've used Ferrea products in many many classic cars, and never have to worry about engine failures.

https://www.ferrea.com/

cheap parts have a way of failing long before you are ready to overhaul the engine again.

just my 2 cents.

Z

 

Easiest option would be engine from Lincoln, if they fit.

 

There will be many 4.2 XK8 engines available, and a lincoln will not operate with the Jag ECU.

 

An '04 would have the later 4.2L AJ34 engine. It came from the factory with metal tensioners, which I suppose can fail as any part can, but it is not common at all (as opposed to the earlier plastic versions). I would definitely firm up the diagnostic before jumping to conclusions. I believe there are cheap USB bore cameras that can be used for inspection through the spark plug holes. That might confirm suspicion about the valves and/or impact on the pistons. On that engine, I would double check everything fuel related first. Any fuel smell in the oil?

 

Ya, the 4.2 shouldn't have tensioner issues or anything like that- more like maybe an overheat issue? Let me know how you get along- I have a 130K 4.2 from a 2004 XJ8 and am trying to figure out if I can plug and play the long block (YAY one days work)or if I have to replace the mid plate and sump. (BOO three days work)

When I do the swap, I do not have plans for the old engine so I may just part it out. (makes knocky knocky noise on startup- vvt issue) but still runs like a champ.

 

Did you perform a compression test and if so, what are the readings?

Is the MIL on and if so, what DTCs are stored? Post them here.

 

Plan:
Codes
compression test
2 "bad connecting rod bearings tests" (screwdriver thru spark plug hole and crank turn click)
timing chain jump check (not sure how, there are no timing marks)
valve clearance check

 

The camshaft flat areas align when the timing is correctly set. Remove both cam covers and check.

Do not rotate the engine in an anti-clock direction when viewed from the front of the vehicle as damage to the main and rod bearings is the result.

 

I will have to make cam holding tool. Ford 4.6 engines don't have timing marks, I used vise grips to hold cams, it was long time ago.