So, my intention is to get a donor car (probably something that has been in an accident) and replace the engine, gearbox and as much as I can in my 1977 XJS with the equipment from said wrecked vehicle.
At this stage I am trying to find out as much info as possible about what problems I may or may not end up stumbling across. I should note, that this is a long term kind of thing and I am just in the research phase at this moment.
The most likely candidate for this swap is the AJ34S, the AJ133 Supercharged would be the dream choice, but I will probably end up settling for the AJ34S because of price and availability.

I am aware that the norm for engine swaps involves American V8s, but this doesn't really interest me. I know it would be cheaper and easier, but that is not the point of a Jag.

There is a rather long list of things that I intend to change about this Jaguar, but the primary things are:
1. Engine and Transmission.
2. Rear differential to allow for outboard brakes. Probably from a later XJS, there was another Jag that had the same setup I could use but I have forgotten the name.
3. AC system.
4. Interior.

This is ambitious, will likely take years to complete and will cost me blood, sweat and tears. But it is something that once completed will be very much worth the hassle.

Cheers,
Kaine

 

cool man, once you get it all stripped you should have plenty of wiggle room. Really it is making the mounts to make the engine and tranny work, getting the proper driveshaft, and setting all the computer and electrical systems up properly that require the most work.

Try to get the V8 as far back as possible without being inconvenient so your weight dist. is good.

The supercharged version would be a direct drop in were you to save up for one later on

 

Your biggest issue is probably going to be be the exhaust on the driver's side. The XJ sedan steering shaft is in a spot that makes it difficult to find headers or exhaust manifolds that fit. I do not know what the Jaguar V8 exhaust manifolds look like... or how many versions of said manifold exist. You could be lucky and they might fit! If I were you, I'd get some pictures of the manifolds and compare them to other V8-swapped cars that work. As you mentioned, the vast majority of these cars are GM engines. There might be some Ford and Jaguar swaps floating around. See what all of these people did for exhaust manifolds on the driver's side.

The second biggest hurdle you're going to run into is engine management. More specifically, if this is the path you choose, how are you going to convert that Jaguar V8 engine harness and ECM to a stand-alone system? I'm sure it's possible, though I'm not sure how well documented it is... or maybe you're planning an aftermarket engine management system?

Engine mounts would be the last on the list. Getting the engine and trans in the car, in the correct location, and most critically - the correct angle relative to the differential input shaft - might take some time. I suggest making an adjustable transmission mount so you can adjust the angle once it's in the car.

I think those are the big-ticket items. Everything else (fuel, cooling, power steering, driveshaft, throttle cable/drive-by-wire throttle body, trans shifter linkage, etc) is very manageable. However, it will be much more difficult and time consuming than doing a high-quality known swap, such as an GM LS-based engine swap, mostly because there just isn't a lot of information and support out there for the Jag V8s like there is the LS-based engine family. If you hit a wall there might be nobody that can help you. Think of the gravity of that fact for just a moment!

As you said, yes it is an ambitious project. Do as much research as you can before you take the plunge and map out as much as possible. I did an SIII XJ6 LS-swap before the kit became available and it was a huge undertaking. It took 8 years of work before I drove it for the first time. If I had to do it again, I probably would have done a much less ambition and more conventional & well documented swap. I would have spent more years enjoying and driving the car, and less years working on it.

I don't think it's fair to say there's a single point to a Jaguar! I know mine has served my purposes of providing great enjoyment over the years... Jaguar engineering, LS-engine and all!

 

Man, a supercharged Jag V8 in the XJS, now what can be more desirable than that! Such a car would be a total dream-come-true and I wish you all the very best in your project.

I once read an article about this NZ or So. Africa company where they installed the whole running gear from an XKR into an E-Type, even including the whole dash assembly. If I'm not mistaken, I actually saw (I believe the same people) exhibiting in a booth here at the LA Car Show, a few years ago. They confirmed that they could do the same with just about any Jag. If they can do it on an E-Type, or any Jag, it can certainly be done on the XJS, I'd say.

Good luck and keep us informed.

Cheers,

 

The mounts aren't much of a problem, in order for it to be registered for road use, I have to have a certified mechanic attach them and then verify them, so it won't be much trouble, just money.

The plan is to have as much space in the front as I can get, because of the way the bonnet flips it makes working on it somewhat easier, and obviously helps with the balance of the vehicle. Plus I would prefer to have the battery in the front, so that will also help with having more space.

I'm not inclined to get the non supercharged version, purely for what it will cost me, since it would essentially double the cost I would end up paying for the parts, or pretty close to. Unless I could find the 5.0L version, then I might look at Supercharging that engine instead.

The exhaust is definitely a possible concern, and is exactly what I was hoping to find out now. Worst case scenario I can have some custom headers worked up, there is a place in the nearest town that does custom exhaust systems as well as bolt on aftermarket ones, they did an excellent job on my Verada. It will cost something nasty, but as a last resort they definitely know what they are doing.

The EMS/ECU/ECM is not an issue. The intention is to use everything from the donor car, so the wiring harness and (probably several hundred) sensors, as well as everything else that the ECU runs will be a part of the install. Where possible of course. I don't really want to have to use an aftermarket ECU as I don't know anyone who does that kind of thing, but it is my backup plan if the first option is not practicable or feasible.

I am definitely happy to leave that part to a certified mechanic, definitely don't know enough to do it myself, and whilst I do knew a decent fabricator, I would be much happier to know that I could have someone to yell at if things go wrong.

Whilst I am not arrogant enough to think that this is breaking new ground, I am arrogant enough to think that this can be accomplished by me and the people I know. It is a sobering thought, that I might get stuck and have no way forward, but I don't think that this is going to happen, since I am essentially rebuilding an S-type R or XF Jaguar in an XJS body. Sure there will be complications, it will take money, time effort, money and probably some money. But I don't need this done tomorrow, and if I had it now then in all likelihood at my age, I would probably end up doing something stupid in it. Well not probably, definitely do something stupid in it.
Right now I have a car I enjoy driving, (wouldn't have it otherwise) I have time to plan and work out the annoying details, and as you say, not committed to either solution. But I am going to give it a shot, so we shall see what happens, my utter failure or grandiose success will be documented here for all to learn from, hopefully it will be the latter!
Also, thank you!

I wasn't trying to offend or anything, just having a go at how old Jags tend to be a pain in the *** as much as they are wonderful. I am sure an XJS with a nice US V8 would probably do everything I want, but it's not something I really want to do. I would like to keep a Jaguar engine in my XJS, even though it will be a PITA.

Cheers mate, I hope it is a dream come true, not a nightmare come to life.

I would have to agree, but I would hate to see how much they would charge for it!

 

I hate to shoot down your plans, but sorry mate, you are really underestimating the complexity of the modern vehicles. Assuming you mean a 4.2L S/C XF, XJ or XK as the donor, then it will have to be a complete re-body, no shortcuts, no leaving stuff out, every single electrical component will have to be transferred, including the instrument cluster.

And you will have to use the exact same diff ratio as the donor car, the stock ECU does not allow you to use a different ratio, at all.

A standalone ECU would work to run the engine, but the transmission still needs to be run, if you get a 4.2L donor with the ZF 6HP26 you will not find any standalone TCM's that will run that transmission.

My suggestion would be find a wrecked 4.0L XJ or XK, the electronics are much more basic, and the CANBUS system has already been cracked (jaguarspecialties.com)

You might be able to find someone who can reprogram the 5-speed Mercedes transmission from the 4.0L XJR/XKR to run with a standalone ECU, but there is no-one who's done this for the 1st gen 6HP26 in the 4.2L cars...

Or you will have to look at a manual conversion, using the 6-speed from the diesel S-Type (check xkracers posts on this).

Lots of late-model Falcon & Commodore drivelines, including a modified stock ECU, have been swapped into earlier cars, but believe me, this is impossible with the Jag electronics.

EDIT

I thought about this a little more....

If you are dead-set on using an AJ33S or AJ34S, along with the ZF 6HP26 transmission, then talk to some of the local Ford guys who have done conversions of the FG Falcon Coyote 5.0L supercharged driveline into older cars. You could possibly use a modified FG ECU and management system to run the AJ-V8, and since the Fords also use the ZF, then putting the Ford TCM into the Jag transmission, so it would talk to the modified Ford ECU, might just work.

Essentially it's using the management system from the Falcon to run the Jag driveline. And since the Ford management system is pretty much cracked, you will have a much better chance of making that work.

 

That really was the intention though, taking the XJS back to just the body, and transferring everything accross. Which would mean essentially rebuilding the donor car into the XJS body. I kind of figured that would be the only way to guarantee 100% that the finished vehicle would actually be viable.
What I don't know, is how much of the electrical components are tied to the ECU, or perhaps I should say, which accessories are tied in. Power windows for example, boot control, electric seats that sort of thing. Stuff I may not be able to transfer. But it was always part of the plan to re-make the interior using the donor parts, especially the Instrument Cluster. I could very well be underestimating it's complexity but so far it doesn't seem like it.
And yes, I do mean the AJ34S. Or the AJ133 Supercharged. But the former is more likely taking availability into consideration.

So I either have to work out how to make the entire rear assembly work in a narrower (I assume) car, or simply change the crown wheel and pinion to suit the required ratio. Though I am curious why the ECU would not work with a different ratio, and how it would even know?

 

On the later Jaguar cars EVERYTHING is run by the ECU. The car will not even start if (eg) it detects that the ignition lock assembly has been changed and the ECU has not been updated to tell the ECU. Every single component has an electronic identifyer that the ECU checks everry time. The car will know about the diff because the road speed (via the ABS) will not jive with the speedo/revs etc etc. 100% rebodying using 100% of the electronics from the donor is the only way to go as Monsieur le Moderateur said, and NOTHING can be left out. And good luck getting all the loom out and working from a crahsed car. Once done, you are then stuck with needing the full Jaguar diagnostics and genuine bits to fix anything - further nightmare. In all the club magazines (eg JEC mag) just about 100% of the problems written in about on the AJ8 powered and later cars are electronic. Often on quite new cars and often problems that the main dealers cannot fix. Tiny wires fracturing/failing all over the place, it makes keeping a V12 going seem like maintaining your lawnmower by comparison.

Installing a Supercharged 6 cylinder from a 9às saloon is doable. Your project can be done, but only a really expert specialist who really understands all the systems in the later cars could do it. Sorry, but that is the reality.

Greg

 

Just to give you an example, here are the complete wiring diagrams for a 2004 model XJ http://jaguar.bttlxe.com/xj/2004%20XJ.zip

Have a good look through them, take your time.

The XJ has four different digital networks running various modules and functions of the vehicle, in addition to the good old fashioned analog wiring that runs everywhere too.

The instrument cluster is the network gateway, all four networks run from there. There are up to 21 separate modules that run on these networks for the car stuff (depending on options), plus up to another 7 separate modules for the entertainment/communications system (which you could leave out)

There are a few other modules that you could leave out, but the problem is that if you do, even though the driveline would run (without restrictions on performance) the instrument cluster will be throwing up error messages all the time.

And as for the diff, yes you would have to run exactly the same ratio as the donor car, otherwise the transmission thinks there is a fault & the car goes into restricted performance. Believe me, i've been trying to find a way around this for a couple of years now....

 

Doable if you use a standalone engine management like a mega squirt to run fuel and spark and megashift to run the trans. If you wan to use the stock control units you'd be better off doing a re-body of the later car. That would be easier. I've seen a few of these, most recently I saw a what I think was an 60's impalla bodied over a BMW 750il. It was well done but interior looked odd.

 

Probably should add, I do have unlimited access to an electrical engineer with about 30 years of experience in this kind of thing, plus 45 years of working on British cars, and he is telling me to pick your brain as it seems you have a working knowledge of the systems we are going to be working with, do you mind?
Thank you for the wiring diagram, that is something I can study when I have some down time, give me a better idea of what is linked to what and where.

He also seemed quite happy about it running digital networks, the analog stuff is a piece of cheese but the digital network does throw some complications but nothing that can't be worked around, and it may end up doing us favours.

The ET/Comms system is of no interest to me, a better system will be installed anyway. The airbags are a concern though, it may not be practical to include them in the install, and if they run off of the Digital Control Bus, well that would probably be an issue.

Do you mind sharing what you have done or tried with the diff?
My source posited that in all likelihood there would be a sensor on the output shaft of the transmission for speed sensing, irrespective of the transmission ratio. Would it seem possible to install a varistor on the DC side of the sensor to modify the voltages that the DBus would be transmitting to the ECU?

 

I still don't think you understand the complexity of using the stock electrical system.
This caught my eye: You have a friend with 30 years of experience that can't reprogram the ECM to work with a different gear ratio? I'm not sure if that speaks to your friend's ability or the Jaguar ECM's inflexibility, but it's certainly a red flag to me.

To make this work properly, getting a stand-alone ECM and TCM would be your best bet. You'd get all the Jaguar hard parts you want (engine, trans) and have far more control over them than anything you could cobble together with the stock Jaguar electrical parts. You'll have less invested and a better overall finished product both aesthetically and functionally!

 

If your guy can't figure it out from the wiring diagrams....?

Diff ratio problem here https://www.jaguarforums.com/forum/g...ids-sdd-77299/

Long story short, there are two speed sensors in the transmission, and speed is also measured by the ABS wheel speed sensor, right rear.

The ECU & TCM compare the wheel speed, to the output shaft speed, to the selected gear, to the input shaft speed, to the engine RPM), to what it should be under normal working conditions, and when something doesn't match up: Restricted Performance, & you're going nowhere...

If you change any of the sensor signals, it throws something else out, the only way is to change the programming in the ECU/TCM, the "what it should be" value, which nobody can do...

No big deal if you can find the exact ratio to suit the XJS diff...

In all fairness, it is the inflexibility of the Jaguar ECU/TCM. Most people are shocked to hear that there is no way of getting around this. Even the very experienced ones...

+1 to that, but if all else fails, send your XJS over the Tasman and get Beachams to do the conversion... BEACHAM

Beachams use the 4.0L X308 XJR as a donor, which as I mentioned before, is much less complicated, and the bus systems have been reverse engineered....not so for the later models.