I like the Jaguar V12. Quiet. Silky Smooth. Perfect for its time. But by contemporary standards, it's antiquated. It's down on power, and the 3 speed transmission is positively anemic. Yeah, even the 6 liter + 4 speed is relatively slow.

Let your imaginations fly. Given say a $25k budget (not bad I think seeing you can get a nice XJS for $3k or less if you're patient):

- how would you modify your XJS for modern performance
- what would you transplant into your XJS for modern performance

For argument's sake, SBC (really any Chevy or Ford) is excluded. I'm talking Maserati, Ferrari, BMW, Mercedes V12 engines and transmissions: something worthy of being in the XJS chassis. What would you substitute? Throw out some rough figures (cost, performance numbers), and rationale.

I'll start:

what: 2003-2006 Mercedes twin turbo V12 (search [{manufacturer} V12 engine] on ebay) $3k
why: proper breeding (Mercedes)
why: proper # of cylinders (12)
why: proper power delivery almost 500HP stock (smooth as hell)
why: ECU tune gives Lamborghini killing power (700+ HP & Torque)
why: transmission with proper ratios and performance $1k

Would it fit? No idea.

Would it rock? Definitely

Second choice would be an '02 BMW V12.

Third choice ... twin turbo existing V12 and stick a 4 speed auto behind it.

Nomex undies on

 

how about a ls motor which is twin turbo charged..25-30 mpg and fast as hell..I like the idea of a v12 in my car but my gas station likes it also, second this car could not spin the tires on wet pavement. Jaguar really blew it packing a whole 200 plus horses under the hood and 12 mpg..

 

It might be ME needing the flame suit after everyone reads this.

For $25,000 I'd be sorely tempted to simply go out and buy a car that already has a modern engine and the level of performance I want.

I guess I've gotten dull and lazy with age !

Cheers
DD

 

If you have an Jag V12 that performs as you describe then, respectfully, I'd say that there's something wrong with it.

My '88 XJS V12 would burn rubber on dry pavement and the throttle had to be carefully feathered if the roads were wet....and delivered 20 mpg (highway driving, that is!)

Cheers
DD

 

I think this would do nicely:
Dodge Viper Engine Viper Specialty Race Motor Gen 4 8 4L Vin Z | eBay

However, my fantasy is not to put another manufacturer's motor into my XJS. It is to use one of my V12s and XJS front & rear suspension as the foundation for a car I have already designed, and will build from scratch when time and funds allow.

 

I agree with Doug. My totally stock 89 XJS V12 would turn the tyres on dry road with the 2.88 diff, now with the 3.58 it will really light the rears.

 

I looked for.these twin turbo v12s on ebay and saw none for 3k

 

but if were talking swaps, take a rb26 skyline motor and a.large turbo and.make in the upper 700 range.
why because it's badass,
and it's an inline 6

 

you guys got it all wrong!!!!

AUDI V12 diesel ,comes with twin turbos and intercoolers, stock from factory 500HP, but yes, 700 lbs ft torque,(torque is what you use to pass someone or pull away from a stop).

now recent ECU chip modifications, can make the stock engine make 650HP, with a neck snapping 850 lbs ft. torque starts at 1700rpm and holds it all the way 3500rpm, by then you got them all beat. 2.88 wouldnt be enough gear, need another overdrive, for a final ratio of 1.95 to 1.

it is actually lighter than a Jag V12 6.L, by 30lbs complete.

i think mated to a PROPER GM 4L85E with a good TCU.

that 2.88 LSD would beg for mercy, maybe find the drive line weak spots.

YUUPP!! that is what i would do if i had the money and time(i got plenty of that,retired).

according to my calculations ,MPG would be in the 28-34MPG, cruising.

yeah i know i'm out of the box ,as usual! LOL.

none of those other choices got any torque worth worrying about, there all about hi-RPM

 

turnin tires dont win any races, but does make a good show!

and i shoulda bought more than one of these t shirts. in 1989.

 

Humpf! Well, damn it, MINE won't spin the tires, and I rather wish that it would!

87 V12 5.3 with 63,000. I've even put cold air intakes in it, so it should be at least slightly more powerful than stock.

I can spin them on wet pavement, but so can my wife's Camery :-(

John
1987 XJ-S V12
63,000 miles

 

well ron, if I ever decide to cut up a new.audi or take out a massive loan to build a jaguar xjs I will use an audi tdi v12

 

Some good ideas out there! Never considered a diesel, but they have come a long way. The Audi is probably straining the budget already though.

I need to figure out how to post pictures here, so the links don't break as auctions end, etc.

And I agree that a properly running XJS will light the tires all day long and definitely requires respect in the rain.

Currently there's one twin turbo mercedes V12 @ $3900 asking.

2003 2006 Mercedes Benz S600 CL600 SL600 Factory Twin Turbo Engine Motor V12 | eBay

 

ignore

 

Ron, I wonder if Lambo built an Aventador with that diesel engine.
Not sure you could put one in an XJS for $25K? I wouldn't want a live axle in the back.

I think I'd spend the money on better breathing etc on my 4.0. Aim for 340 bhp, and put the rest of the money into a wider body.

 

To be fair and honest mine wouldn't "light the hides" as seen in Ronbro's pic !

It would certainly leave two black stripes on the pavement....but not quite like *that*

Cheers
DD

 

For starters make sure your vacuum and mechancal advance system haven't given up the ghost.....and that your base timing isn't retarded. Spec is 18º BTDC @ 3000 rpm

Cheers
DD

 

My 90 XJS was dyno'd at 238ish HP at the rear wheels which should be about 285ish at the flywheel so it is within factory specs. With the older 15" tires installed it would if pushed light up the tires. Not fantastic mind you but it would do it. I now have 17's and it won't spin the tires on dry ground in a straight line. I can say that with a good set of rubber in any correct size a stock 5.3HE won't give you a good burnout if any. My suggestion is if you want to do burnouts, buy cheap tires.

 

If you can't spin the tires on your XJ-S I agree with Doug (base timing, vacuum and mech advance plus that vacuum advance has been known to get hung up on a wire in the dist)) also check you are actually running on all 12 cyl's...very easy to be on 10 or 11 and not even notice it. Mine WILL spin them and will light them up if I hold the brake even with the 2:88 rear and new sticky tires.

 

Apart from the Tech aspects covered by Doug et al, why would anyone want to send $$$ up in smoke?

For $25k I would be buying something more modern for this purpose.

At $6000 I was involved with a AMG 560 MB SL rag top from Japan, from the mid 90s, I felt that it would certainly blow away any XJS from the same period.

The 7.3litre V12 was something else!

All this only 5 years ago.