Hi All,

This is my first post. I am wondering if anyone has ever tried to swap the v12 for a supercharged 4.0? I am looking at an 88 xjs with blown head gasket. Body and interior are excellent. Owner is letting go cheap. Would a 1998 xjr engine and transmission be a possible swap? Anyone ever done or explored this configuration? Any insights would be appreciated.

Thanks

 

I believe it has been done with a 6 cylinder. The 6 cylinder XJR engine is a much better candidate than the V8, simply because the electronics are much more integrated on the V8 cars. The ECU for transmission and engine are stand alone units on the 6 cylinder, they are networked together along with everything else on the V8.

Also, since the AJ16 engine was used in the last XJS cars, the motor mounts are a bolt in to use the 6 cylinder.

I've spent a lot of time with the electrical manuals for both the 6 cylinder and V8 XJR cars for a different swap, and concluded that the V8 was impossible to retrofit without very major work - either custom ECU's or taking everything from the V8 sedan and transplanting it to the XJS shell.

 

Thanks Jagboi64 for your intelligent response. The 6 cylinder is not something I thought of but makes complete sense. Now the hunt begins.

 

One thing to be aware of is the later cars have a different hood (bonnet) with a taller "power bulge" than the earlier cars. I don't know if the 6 cylinder will fit under the lower bulge. Low bulge on the green car, tall on the red car.

 

I have seen an XJS with the I6 XJR engine installed, there was one for sale here in Australia last year, so it is doable.

 

It's very hard to retrofit an XJS and or Seres 1,2 3 XJ with any engine that has a front oil sump. The AJv8 has a front sump so it would be necessary to extensively modify the XJS cross member for clearance. Many LS engines have front sumps but there are aftermarket rear sump kits that make retrofitting easy. All SBC's are rear sump so these are more commonly done conversions.

There are many other reason why the AJV8 is not a common conversion. They include different drive shaft technolgy, drive by wire throttle can be finicky, NO aftermarket engine and transmission control support and, high cost of replacement parts. Also the early AjV8, of which many are available, are not great engines to begin with. They're ok but not simple and reliable like an SBC, LS or AJ6. As for the supercharged variants...the plumbing for the inter-cooling is also very daunting to transplant. Furthermore...400 HP is easily and more reliably attained with a SBC or LS then with an AJv8 transplant.

 

Yazmaster,

You probably know that most of us Brits are very biased when it comes to changing engines in XJSs! However if you're going to do it, and not thinking of putting another V12 in there, (which is the easiest option) a supercharged AJ16 from an XJR would be an interesting project. The key things for you will be the bonnet (you need the bulge bonnet), the air intake (you'll need to fabricate one), whether it's possible on a LHD car because of the steering rack route, the wiring looms (sadly it's much easier to start with an AJ16 XJS, but I'm sure anything is possible) and finally the ECU. The ECU from the XJR is linked to the x300 security system. There a few ways around it, including getting a bespoke engine ecu.

It's been done a few times in the UK, including one with a manual box which makes for a rapid car!

Good luck

Paul

 

The AJ26/AJ27 will fit, but it requires a LOT of work to get it in there and running. You'd be better off chucking a LUMP in there instead. More power, lower complexity...

 

Hi Paul,

Thanks for your response. I'm on the east coast of Canada and my mechanic (I sadly have no mechanical skills whatsoever) is an old school Jag guy and would not entertain doing a swap other than using another jag engine. I'm know when I run my idea by him, his blood pressure will surely rise. I love the look of the pre facelift xjs but am interested in having a gentleman's sports car rather than grand tourer. I think this could be a worthwhile project without breaking the bank too much.

 

The North American XJR's did not have the immobilizer system that the rest of the world did, so starting with a NA spec ECU is easier.

 

Good for him! Certainly the cheapest and easiest thing to do is to replace the headgasket on the V12. It won't be cheap, but relative to doing an engine swap it would be. There are things you can do to liven up the V12 a bit as well, take a look at AJ6 Engineering's page.

 

The cheapest way to get an XJS with a 6 cylinder engine is to simply buy one. They usually cost more than the V12 versions, but way cheaper than a swap. You can search for 'Jaguar XJS 4.0 Coupe site:craigslist.org'. Plus you get to enjoy driving instead of working on the engine.

Personally I love my V12 Jaguars. That V12 grin when you go from 0 to 60 in first gear is priceless. And unless you drive it every day, gas mileage doesn't matter that much.

BTW: Please don't put a 350 Chevrolet engine in it. There are already lots of those projects on Craigslist. Usually half the stuff doesn't work.

 

No worries Andreas. Would never dream of swapping the v12 with an American v8. Its a sickening thought really. I like the v12 as well but the idea of taking the xjs to another level using proper Jaguar technology is intriguing.

 

if intriguing = expensive, then yes.
I'm thinking Mercedes V12 is the answer.