Hello all!! Just recently acquired this beautiful 1996 XJS 6.0L V12 convertible. Previous owner and I worked out a deal as it hasn’t been running in a year. It’s got lots of goodies with it in the trunk so I’ll be starting the journey of learning about the V12’s and how they work.

Would like to have it on the road within the next month running & driving.

 

Congratulations. I don't know the exact number, but there weren't a lot of 1996 V12s produced. There is plenty of help available here. You may also want to peruse Kirby Palm's XJS book: https://www.jag-lovers.org/xj-s/book/XJS_help.pdf

 

Will do and much appreciated! I’ve got a 2006 S Type R I’ve done plenty of work too, but the V12 is a whole new beast to me. Will do lots of reading up. Here are some of the parts I’ve got with the car. New wiring harness for the injectors and ecu as well as some other goodies.

 

Picture of the engine bay

 

Picture of the engine bay

 

What are the last 6 digits of the VIN? The ABS reservoir and system shown is incorrect for a 1996 car. The 1995.25 model year and up cars got the later Mark IV Teves ABS system with a triangular brake fluid reservoir with a conventional brake booster and master cylinder.
Also, if the 10th digit of the VIN is an "S", it's a 95. It needs to be a "T" to be a 96.
A 95 and 96 car would also have 20 spoke alloy wheels as delivered.
Jon

 

Last 6 of the Vin are 190328. Wasn’t sure if it was a 96 or no as I was going off what the previous owner told me.

 

If the 10th digit is an "R", it's a 94.
so:
R = 94
S = 95
T = 96
​​​​This is for US spec cars. Euro spec cars have a slightly different VIN arrangement.

Jon

 

If the 10th digit is an "R", it's a 94.
so:
R = 94
S = 95
T = 96
​​​​This is for US spec cars. Euro spec cars have a slightly different VIN arrangement.

Jon

 

Thought I’d include some more pictures for viewing pleasure. 10th number is an R as you will be able to see below from the vin. Just put the new distributor cap on it and plan on looking up wiring diagrams and the like so I can put on the new injector harness as well as new ecu wiring that I have waiting for the car. Hope to try and tackle that tonight.

What are the right fluids to put in the V12? Engine Oil? Coolant? Should I run premium? I’d like to put all new fluids in it this week as well.











Old distributor cap off

New distributor cap on

What I believe to be the throttle cable

Bits of wiring from it 😳

Full vin of the car

 

Yes, premium gas. Oil is 15w or 20w-50 oil. This is not a modern engine, so it requires heavier oil. I happen to use Mobil 1 15W-50. DOT 4 brake fluid; standard DOT, not LV. A modern antifreeze that works well, and is recommended for use in modern Jags, Mercedes, etc is Zerex G50. I get it at Auto Zone or Advance Auto. Whatever you do, use an antifreeze design for aluminum engines. And only distilled water if you don't use pre-diluted antifreeze. Bleeding of the cooling system properly is ESSENTIAL. Easiest to do with the nose high in the air as possible. Fill header tank to full first, seal, then fill up the center filler by the A/C compressor. Bleed to radiator at top left side.
Transmission is a version of the 4 speed GM 4L80E. It uses Dextron fluid, and standard 4L80E filters. HOWEVER, the trans pan gasket is NOT a standard GM part. For some dumb reason, they use a non-standard pan shape, and only a Jag (maybe Rolls Royce also) pan gasket will fit. You can get them from Terry's and others. The internal tranny solenoid wiring harness is also unique, but I found a guy in Canada who makes them on ebay. Rolls Royce also uses that harness. They get brittle, and connector locks break. Uses standard GM solenoids.
Diff fluid is 75W-90, but make sure it has a limited slip additive in it; most modern diff oils do.
Read up on Marelli ignition issues in Kirby Palm's book, "Experience in a Book." Do the distributor shaft mod, add RTV under the rotor, and ensure your plugs are gapped per spec (.025") to help prevent catastrophic ignition and catalytic convertor failures.

Hope this helps.

 

The car was built around August 1993, even before the 1994 Model Year update. If it was sold to you as a 1996 car, I'm afraid someone was misleading you.

Still a nice car though.

Cheers

Paul

 

Good luck and have fun with your project!

I suspect will will start finding lots of things that need attention, once you get into it.

I bought an '88 Convertible about 2.5 months ago, or so.

Have spent and still need to spend time fixing real stupid things the previous owner did, and have been and am still discovering things that should work, don't.

I decided to eliminate any unnecessary bells and whistles that don't work, which seems to be mostly wiring related (burned out bulb warning, etc).

I am up in the air about the motor, though. I am going to check the timing this coming weekend, if it checks out OK, I know that isn't the lack of power problem, and it will be getting a new motor, as there are several indications there is a deep seated cooling problem the PO tried to counter.

Unchanged (for years) antifreeze, in an all aluminum motor, promotes internal cooling passage corrosion and blockage, which is a spendy fix, I can put a big block Chev motor in, for less than 1/4 the cost of what rebuilding the V12 would cost, as I have had a nice , new 479 CI motor ready to put in *something* for a couple years. I bought my knowing it was a project, and had contingency plans if the need arose.

Enjoy your new toy.

Doug

 

Regarding engine oil, I would recommend taking a look at your driver's handbook and checking what they recommend for the temperatures you experience. Then maybe have a search through the forum. Modern synthetics are way more advanced than the oil that was available 30 years ago.

 

The good news is that as a 93/94 production car you win the engine lottery.
93/94 V’s had the Forged EN 30 steel crankshaft that was treated to a hardening process. The Connecting rods were also forgings from EN 40 Steel .
Later 95-96 had some sintered Iron crankshaft and connecting rods. They are fine for normal street driving. However Racers need forgings since we are at elevated RPM for the whole race.
Ford ( who had bought Jaguar) switched to Sintered Iron doubtlessly because is was massively cheaper to make. Ford really saved a lot of money by selection of venders, whereas Jaguar had always been loyal to BRITISH venders. ( the sintered iron crankshaft and rods came from Germany )
If you ever get a chance to look at a disassembled V12 you will doubtlessly be impressed that such careful engineering was used to build that motor.
Racers typically use special blocks, crankshafts, rods Etc to go racing. With a Jaguar that is not needed. It already has 4 bolt mains( 6 on the rear main) . And every trick to build a strong, durable, motor.
The short stroke is a classic example. Because it’s so short the pistons and rings last an extremely long time. I’d expect 4-500,000 miles is easily achievable before a rebuild is called for.

 

One other point. Modern fuels have 10% ethanol as standard. Do not listen to those who tell you alcohol is bad for your car. There are 2 kinds of alcohol. Commonly used as motor fuels . One is Ethanol. ( the good alcohol- it’s found in beer wine and Scotch etc. )
The other is methanol ( the bad alcohol - you drink it you die. It also does all the bad things alcohol is accused of.
Ethanol is found in modern fuels. It helps to clean the deposits on the back of intake valves. Makes slightly more power than premium gasoline, runs a trace cooler than gasoline. ( Will fractionally reduce fuel mileage). If you’re getting 18 mpg now it will reduce it to 17.8 mpg.

 

Thank you everyone for the information! I’ll be sure and go through it all to ensure I didn’t miss anything. Even if I was told it was a 96 and it’s a 93-94 car I’m quite happy. I didn’t spend much on the car and quite frankly with the reply of the gentleman earlier about how this car has better forged engine bits I’m quite happy with it. I’m just hoping the engine is good as there was a bit of corrosion in the coolant system when I looked down one of the caps.

Hoping the engine is okay but I’m not certain, as when I went to check the spark plugs they were quite tight. Couldn’t get them out with the tools I had so I’ll have to get something more specialized. I’m not quite sure what a rebuilt V12 goes for but it wouldn’t surprise me if it’s more cost prohibitive than a standard LS or similar swap.

 

professionals get over $20,000 to do a small block Chevy swap. You won’t believe the amount of work that entails. Things like instruments ( the tach is set for 12 cylinders not 8 ) and heater, wiring, etc. The Jaguar puts out 30 PSI for fuel injectors but Chevy requires 60 PSI. Or if you go to carburetors it’s less than 3&1/2 PSI
In addition you will need to buy a new transmission. Even though it’s a GM transmission the bellhousing is drilled for a V12 not a GM product.
While internet myth has it fitting, nobody has explained how to get at the spark plugs under the exhaust manifold. ( Jaguar is narrow 60 degree engine while the Chevy is a 90 degree engine. ) Plus the spark plugs are right on top of the engine in a Jag.
That looks to be a pretty healthy looking big block. So it should have as much power as the V12 does, maybe a little more. But you are putting it in a luxury, heavy (4662 pound) car. Add a couple of people, full tank of gas, and you’re over 5000 pounds. Like a Cadillac.
That V12 is really pretty much the same as a Chevy. It’s a 4 stroke engine. It can easily be hopped up. Replacing both camshafts and readjusting valves takes much less time in the Jag than doing the same to a chevy. ( they are right on top) and Jaguar gives you a bracket to mount the timing chains while you’re working on it.
The original engine was designed to be smooooth enough for the Queen to ride in. All V8’s have a second order harmonic That the naturally balanced V12 doesn’t have. And get decent fuel mileage doing it. If you want more power it’s easy work.
Just open up the intake and exhaust. Look at the air cleaner, designed so you don’t hear intake sounds. But costs 30 horsepower same with all the mufflers underneath. They cost you 60 horsepower. If you use just a pair of resonator’s instead of those mufflers you still gained 45 hp.
Camshafts really increase power. Stock the valves only open 3/8ths of an inch. Plus because it’s so smooth you don’t have to put up with the lumpy idle. Cams will add another 100 hp. But require an aftermarket ECU there are plug and play ECU’s or you can buy a Megasquirt and it will learn by itself what is needed.
The real power is from E85. After everything else, that will gain you 10-15% more power. Again you need aftermarket ECU’s and the sensor package.
If you get a used Jaguar V12 it will bolt right in and a Used Jaguar engine is cheaper to buy than a used Chevy. ( less demand ).

If you still decide to swap motors, I’d like to buy your old core.

 

I hope it doesn't come to that for you. I am just giving you heads up that *if* you have an overheating problem, it may not necessarily be an easy fix like a new radiator. at the end of the post is a pic of a clogged up 308 head, for reference. See that white gunk between the two middle cylinders? That completely filled cooling passages necessitating cleaning it out and TIG welding new AL in to replace the metal that turned into AlOX

Good luck on your new Jag.

I also, bought my XJS car at a reasonably cheap price, knowing it had (several) issues and would possibly need a new motor.

Doug

 

Well, heck, here is pic of the plugs, they look fairly easy to get to.

A new TH400 trans good for 600 HP is available from Summit for about $1500. A complete BBC installation conversion kit, which includes a new radiator is $2300, it also includes long tube headers fitted for the XJS if for some reason the cast manifolds I have don't fit, and those have as easy plug access as the manifolds.

Some one already hacked up my hood real good, so elevating the center to clear a carb won't be doing any disservice to it, plus I can get some of the extra vents closed up at the same time. Tach isn't an issue, I believe one must add a resistor, but in any case, its an easy fix. Putting a big Chev in is probably less work that R&R the V12 (plus having the V12 rebuilt).

The PO already messed with my fuel pump, so a Carter 5 PSIG pump is a real easy install. (the Holley carb works on 5-6 PSIG inlet pressure).

In any case, that BBC I have is a 6500 RPM capable motor, 3.76" stroke, 4.50" bore, very similar to late '60s Can-Am Chaparral BBC motor in that architecture, but with hyd roller cam, and only 10:1 CR. Its something I have had most of (all new parts), for about 30 years, I put it together a few years ago after getting tired of having parts here and there..

Engine Analyzer says 600 HP and 510 ft-lb Tq (max) at the flywheel, usable RPM range from 1000 RPM to about 6000 RPM. Torque at 2000 RPM is 450 ft-lbs. A 2100 RPM stall speed converter should be about right

No, it won't be as smooth as a V12, my old '76 XJS didn't have much oomph down below but once it started winding, the power "accumulated" so to speak, very smoothly.

No, it won't please the Queen, but her *** won't be in the seat, mine will be

And yes, I will let you know if the V12 is coming out.

Doug