1999 XJR V8 Heads

Hi All, Could anyone tell me what the casting number on the side of the super charged head indicates. the problem i have is that for some reason the valve seat dropped and has driven itself at an angle back into the casting damaging the ali! I have looked on Ebay and there are a few heads avalable with the last to digits insted of being “AD” as in my case, they are AE ! My question is would that indicate it is different to mine or as I am hoping just a later casting date or is it possibly valve size difference or even cams are higher lift on the supercharged model The full number on my head is XR83-6CO64-AD. The damage seems to be limited to the seat area as the valve closed it pushed the seat at a slight angle into the port having sliced out a chunk of ali so compromising that port. Many thanks Dave Barnard.

Jaguar issued a TSB about replacement heads.

Any 4.0 head casting should work if the VVT oil gallery is modified for either SC or NA.

The Intake cam is the factor as to it’s application. (AJ26, AJ27 or AJ28 (S-Type))

303-31 VVT cylinder heads.pdf (42.7 KB)

Good day,

I’ve been researching V8 heads lately, because a shop called me for a used replacement RH head for a '99XJR that got overheated, and is cracked.

Checking his VIN, it’s an AJ27 engine with car would have a Cam sensor at the back, and of course, no VVT’s.

I have a parts car XJR AJ26 without cam sensor, but as there’s no provision for Cam sensor, I assume that would not work.

Now, if I undstand the TSB correctly, a NA AJ 27 head, with oil gallery plugged off to the VVT, will work on an AJ27 supercharged motor?
The hole at the front where the VVT pokes out of the cam cover would have to be plugged as well.

Thanks you for considering this, on behalf of the fellow trying to fix his car, and me.



Correct. Any RH AJ27 head with the oil gallery plugged will work.
I think the SC sprocket will bolt to the cam already in the good-used replacement head so the valve lash should be close or maybe need ‘tweeking’ (moving shims around?)

You could also use any RH AJ28 head (4.0 S-Type) but the intake cam is different and you would need to install the AJ27 cam and then adjust all the tappets.

The AJ26 lacks the RH CMPS so it is not worth considering if you need the RH CMPS.

The North American XJR used AJ26 hardware/software and throttle setup and did not change until MY2000 but if you are sure it is AJ27 then proceed.

That’s a pretty cool bit of info there.

Thanks much!

For anyone following, the VIN break from 1 CPS to 2 is A853935. Late '99 build, 2000MY.

I’ll let you know how it goes for him, on the head swap.