OK I've been thinking about this for a while... it's not too hard to find a cosmetically nice XJS with a shot engine for cheap. At first I thought, find a wrecked 6L power train and throw it in there.

But then I started looking on eBay:

v12 engine | eBay

Just search "V12 engines" and sort via price: highest to lowest. Then I started thinking about BMW V12s, as I had an E38 750iL for a while, and it was a slick beast - used to drive it all across Texas - that thing was like a silent cruise missile. That would be an improvement on the Jag, but it's still a little down on power at ~320 horses. It's a LOT quicker than the Jag though, thanks to a modern transmission.

Then I looked at Mercedes V12s of the era; conservatively rated at 389HP, and practically bulletproof - just make sure you replace the (literally) biodegradable wiring harness for ~$600. Now we're starting to get somewhere.

THEN I see that the '03 + twin turbo V12s and transmissions can be had for about the same as the previous generation! Now we're talking. 493HP V12, with an ECU swap pushing close to 600HP and MONSTER torque figures.

I'm thinking this is the route to go. I know Ron likes the Audi diesel swap, but the only time I've ever seen one for sale, it was around $10k and climbing. I've seen Mercedes complete engine & tranny sell for less than $3k.

So I'm curious about two things - if you guys were to (or already have) LUMP, how would you go about it?

And anyone know a mechanic in the Houston area to start this conversation with?

Cheers

 

If money is no object Lamborghini Murcielago Roadster 2005 6 2L Complete Engine Motor J070 | eBay

 

BBC. 475 hp 500+ torque

 

Heh - unfortunately $ is a consideration, but that Lambo engine is cheaper than I would have expected! Also not sure if it would fit the GT nature of the Jag.

Bc, have you done any long distance driving in your conversion? What are your impressions vs stock V12 (don't remember if you did your swap immediately or not)?

 

If I was to build an lump XJS I would look at the drive train from a 2012+ Mustang GT. The Coyote engine has plenty of power but can also easily be fitted with a supercharger or turbo.

It would not be crazy expensive, have excellent power and be easy to service.

And being Ford it would have a passing acceptance mated to a Jaguar.

Mark

 

Flint. I did some good road trips last year. I put on about 3500 km. I have my stroker in there now as a temp while I rebuild my 350. The Jags a bit obnoxious right now. Should have this engine built in a couple months depending on machining cost.
I havent had a V12 for a while now. The V12 is smooth running and quiet. I do miss that. With my 76 XJ12L I didn't trust it to go on long trips. It wasn't reliable. I never drove it farther than I could afford to tow it.
I imagine a long trip with the V12 would be a great on. Not hearing the engine or feel it would be a nice change.

 

Thanks, great info. That's why I'm looking at the Mercedes & BMW drivetrains; I've owned or driven them in their original configurations, and their characteristics (smooth, quiet, good torque off idle but nice rush further up the power band) would match the XJS well in my opinion.

 

The only problem with my dream XJS lump would be that it can't be and it won't be cheap. I've dreamed of a 500+HP, 5.0L supercharged Jaguar engine with the 6 speed (or more?) auto tranny, ever since they came out a few years back, although I'd say that technically it may not necessarily be a lump if it's still a Jag power plant? Wow, my kitty with that monster under the hood, man, that would, indeed, be a dream XJS. But I can't even think of the R&D that it would take to mate such a sophisticated running gear to a '94 car, both, mechanically and electronically; it would be a monster of a project, that's for sure.

But we're allowed to dream...

Cheers,

 

I'd keep the Jag V12, but do some alterations...

Heads from AJ16s, some turbos, increase displacement to 7.0-8.0l, chuck in a good Tremec manual (5speed for more fun) and have some really nice pipework done

 

I always understood LUMP to be Less Upkeep More Power, but yeah it does have a bit of a pejorative slant. So technically I guess it would be a lump, but a fantastic one

Daim, what do you reckon all that would cost? Going to 7.0L, twin turbos, manual, etc. - I'm thinking $40k minimum.

 

I doubt it would be that much... If you have it done, of course, but the biggest problem would be getting the space inside the engine bay to add some turbos... Welding some pipes shouldn't cost any more than say €2000, turbos a piece new €600, engine overhaul and rebore about €5000, custom ECU about €1000, custom heads or better altered heads with cams about €800/piece.

I'd say, roughly, a good €15k should get you all that and maybe even a lot more

 

And anyone know a mechanic in the Houston area to start this conversation with?


If you are paying someone else to do the work on this for you, you cannot afford it. If you are doing it yourself, and your labor is free, it can be an interesting project. Get the transmission that goes with the engine, and get the complete engine wiring harness and engine and transmission control modules. The GM engines and transmissions are the popular swap because they are relatively cheap and reliable and the engineering work to install has already been done. With anything else you will be on your own. Again, an interesting project if you do it yourself, a huge expense if you pay someone else to do it for you. Good luck to you.

 

My Lump would be taking a Late 90’s Chevy Monte Carlo, Black.
Paint a big white 3 on doors, bonnet, boot and roof . Then install a Jaguar V12 tuned to Group 44’s specs.

 

Sell jag. Buy speciically 2002 z06 corvette, add super charger. Beat hell cats.

 

So, if I were to lump my XJS and money was no object.

 

It's been a dream of mine to put an Aston Martin 6.0L V12 in an xj-s. It fits in the new V12 Vantage so it should fit in an xj-s. The AM V12 may be two Ford Duratec V6's glued together, but it's a British marque V12 which in my mind makes it one of the most appropriate options for the xj-s.

That V12 LS engine looks incredible. I'd heard of V10 LS engines but never a V12.