So I have the opportunity of buying back the xj6 that I grew up in as a kid. It has some unknown engine issues (oil getting into spark plugs, could be valve cover gasket but considering the current owner I suspect their some other lurking issues) and if the original engine is on the fritz I was wondering how difficult it would be to swap the XJR6 engine and 4l80e trans into it. Do the computers or wiring also need to be changed? Are the computers vin-centric (Have these on my xc70)? I know it would be cheaper to go out and buy and xjr outright but considering the price of the car (nearly free) and the sentimental attachment from my youth it could be a fun project. It's the car that got me interested in cars and it would be a shame to see it end up in junkyard.

 

I think you still need to go out and buy an XJR - because you need so much stuff off of it: Engine, transmission, intercooler, fuel tank all spring to mind as "must have's" then you'd probably also want the limited slip diff from it, possibly the trac-control as well if sentimental XJ6 not so-equipped, though those are optional, not essential to make it go.


If you want an XJR, you know what you must do; you've already stated it. But if you want to save an aging XJ, oil-in-plug-wells is a much simpler fix than transforming the car. At worst, you are looking at finding a replacement cam-cover (I obtained one a few weeks ago for $17.99; could've been $14.99 if I wanted to turn in the old one) gasket, plug-well-seals and bolt-spacers will run you another $60-80....plus whatever else you find it needs from neglect. These engines are pretty durable, though.
Again, for saving the old XJ; you can obtain a like-kind naturally aspirated AJ16 from a breaker for $300-$600 easily enough....and make the swap.
So it boils down to what your objective really is. But don't forget the oft-quoted idiom around here: "The most expensive Jag is the free one...."

 

Yes, computers are different, as are the wiring harnesses. There are 2 variants of XJR ECU, 1995, and 1996-7. The 95 cars do not have EGR, the 96 and 97 do. Transmission controller is different, and also has the twin fuel pumps in the tank. Rear transmission mount and shift cable is different too.

Ideally, I'd skip traction control ( it's useless in snow for example), but that had a different throttle cable.

Agreed, to do the conversion you'd want an XJR parts car.

 

I think as others have said, anything is possible with enough time, money, ability and motivation. But it may take a lot of all of the above, perhaps too much.

Others have asked about swapping XJR engines into various cars, and in my opinion it probably would be easier to install the XJR drivetrain into another non-XJ6 than into an XJ6 just because it would be easier to start from scratch than attempt to figure out and modify the XJ6 to accommodate all the differences.

While it isn't impossible, my personal opinion is that it would be better time and money spent just to get your XJ6 back to its original configuration in good working order than try to convert it.

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I reckon you could do it but it would not be expedient to do it. If the result you want is an XJR then get one.

If the result is to love the old XJ6 for what it is then just do what it needs and no more. Bloody good cars as standard.

If you happened to have a scrap XJR then it would be a fun project to bring it to life again in the good XJ6 body.