1970 Jaguar XJ6

Some more detailed info.



At the time I did the first transplant, from the XK 2.8 4-sp od to the AJ6 4.0 5-sp, I was not aware of that engine mounts from the XJS are, as I understand it, a direct fit. Only knew that this kind of swap had been done before and that there should be space enough without too much modification.

So, had the engine standing on some piles of wood blocks in what I determined to be the best position. Centred and leaning in what seemed to be the correct angle and with some 20 mm play down to the steering rack. Fabricated the mounts / towers.






For the transmission I used a simple engine rubber pad mount from some Volvo, tapped new threads for it in the transmission housing. The support frame cross over thing was put together using parts from the old one, reinforced here and there.




In order to get the gear shifter to fit as good as possible into the existing opening in the tunnel , the linkage rod, small u-joints in each end if I remember correct, was shortened as much as what seemed possible without affecting function. Some 1.5” was cut away, same with the gear shifter support box. The tunnel opening was enlarged maybe 1/2” towards the rear.



The nice old shifter knob is from the 4-sp. The OD on-off switch would have been cool for operating some nitro shots but is right now wired to handle the dash cam.


The front part of the propshaft, with the sliding yoke, is from the same donor car as the Getrag. Shortened at the rear and bolted together with the old 2-piece rear one. The support bearing and housing is for a Ford Transit, had the same shaft dia. Again, it was a couple of years ago I did this so I’m afraid i have forgotten exactly what parts that was involved.




An alternative to this would of course had been to have a one-piece propshaft made, probably easier but I’m not fully aware of the advantages or disadvantages with the different types. The one I have has functioned ok, has taken quite a stress and fast spinning surprisingly well without any vibrations. And it has not even been balanced.
And, about setting up or adjust the angles, how the eyes in the yokes should be lined and so on, I recommend reading some of the real old workshop manuals, often very detailed instructions.


The rear end has had the coilover units shortened an inch for a lower ride. Problem with that is, own theory, that the vertical distance between the lower supporting points, the small radius arm bushes, and the upper mounts is decreased. The whole unit becomes more prone to twist or rotate under load. Nose of the diff goes up until traction is lost, nose fells down, traction once again forces the nose to go up and so on in cycles. One of the reasons for wheel tramp, a well known problem when the Jag IRS has to handle lots of power.


This homemade HB clone anti tramp bar cured most of that.





Another problem that comes with this transmission/ rear end combination is the lack of speedometer outputs. There are some different solutions to that, I choosed what seemed to be the easiest way, ordered a 4.5” GPS speedometer from Speedhut and had it sit inside the old 5” housing. There is a nice option of customizing the looks when ordering. That’s why the Jaguar logo.
Did not come cheap though.





Unfortunately, there is sometimes problems to have the GPS speedometers passing MOT. Hence the GP instead of GPS in the logo.

The rev counter, Smiths RVI type with ignition wire loop inside, was functional but became more and more unreliable. Most of the electronics is now substituted for a small DIY circuit. Tach signal is from the ECU.




And, talking about passing MOT. A picture of the engine dedicated for those occations, once every two years. The infamous AJ6 2.9.





Used this engine for a short time last year. Coupled to the 5-speed it worked quite well. With it’s bad reputation in mind.
Known to be one half of the V12. Read somewere a saying that Jaguar used the better half of that for the 2.9 litre.
A joke of course!




Believe I have to divide this build story into further more separate parts so I’ll take a brake here.

Will be back in a couple of days with more details on the exhaust, fuel, ignition, cooling and so on.

The Megasquirt thing will be later on. With maps and settings, no problems.