First it was a clapped sad 88 xjs v12, then it was a 98 xjr that blew a head gasket, and finally I now have a 96 xj12. Payed $800 and it's probably the most solid Jag I have had

. Lots of little things but nothing major. Long term plans are to turbo it. Current problems are, occasional surging on a decel, some rough running, blown motor mounts, belt squeak, oil leak, slightly weak posi traction, God damn door panels coming off which makes me want to explode, some broken sun roof parts, and broken tilt column. It's amazing that that's it. I probably won't come on much since forums are horribly clunky and im not a pro. But for my biggest challenges I'll come here. Also the photo uploader is horrendous so that's the only picture you'll get.
Always wanted a v12 sedan. Major obstacles for turbos or fixing the sharp edges on the main caps where these motors break and tuning the ECU through the eprom.

 

Welcome to our addiction.
Forget turbo, it's not happening with that V12 in its current trim. Wrong heads. Way too much work/$'s to install the right ones for turbo.
Contact AJ Engineering they have all the goodies to wake up your V12.
Rough running check for vacuum issues, the ole girl will need all new rubber bits as she is approaching 25 years old.
Belt squeal is most likely power steering related or harmonic balancer if on start up.
Oil leak again most likely power steering fluid.
Never had posi.
Broken tilt column is a belt.
This forum is far better than any other you will find for Jags and knowledge. Get over the clunkiness, me no pro either and I figured it out so it was no longer frustrating to upload pictures which we need many more of your ride. We like car ****. A picture of the back seat will not do.
No idea on sharp edges on the main caps? Please elaborate.
If you get frustrated with the door panels coming loose (I can relate) your in trouble.
The price is right so you are in good shape to start. It will be a long dark rabbit hole but worth it if you see it through. They only made 249 1996 XJ12's and only about 180ish are in the states. Chances are you will never see another on the road.
$800.00 now that has to be rock bottom. $90,000 ish new.
Good luck.

 

Wrong heads? They are prime for boost with their efficient combustion chamber. The 6 liter opened up makes 370hp. So with 15 psi of intercooled boost with the right turbos that should roughly double, should it not? And why does the turbo set up have to cost anything more than a typical turbo set up? Other than the oil scavenge pumps and complicated charge piping. I plan on mounting two cx racing gt2871's where the primary cats are, and the drain tubes will need a scavenge pump to pump oil back into the engine. Charge pipes on those turbos are thankfully small, so routing them will only be just another small challenge in comparison to the issue of engine management.
Oh, main caps. I will make a separate post within this thread.

 

These 2 pictures come from a Facebook messenger conversation with Paul Kobres.

 

Wrong heads.
Combustion chamber shape in the head is not boost friendly. You would have to get some pre he heads and they do not bolt up without considerable modification. Factory is 313 H.P.
Nobody has turbo'd a 1996 XJ12 in stock trim with factory heads ever. There is a reason. Wrong heads!
I also wish it was different.

In 15 or so years of multiple V12 ownership I have never heard of a broken main... but I don't get out much.
Don't get me wrong I would love to see somebody prove me wrong on the turbo thingy. But it's not gonna happen with those heads.

 

Mainly because not many people hot rod v12's. But those that do have well documented the problems. Bonner ended up doing turbos with 20psi and no intercoolers and melted things, duh.

So what about the combustion chamber isn't boost Friendly? You do realize it is the most efficient combustion chamber in a production car right? Im absolutely positive the he head is by far superior to the flathead for accepting boost.

 

I wish you nothing but luck.
I am no expert on turboing anything but I went down this rabbit hole 15 years ago and it's long and dark.
The chamber design will not give you the proper swirl. Combustion will be uneven. The spark plug location is not ideal and is far too recessed. Useable boost will be so low not much benefit.
I'm not trying to discourage.
As mention AJ Engineering is where you will get the biggest bang for your buck. Call them and they will explain in layman terms why this is not happening with turbo's.
Others here are far more experienced with V12's than I but you will never communicate with them on this forum. The X305 site is the dead sea when it comes to traffic.
Post this same idea on the XJS forum and you will get allot more experienced advice on this issue as the traffic is 100 times more than here. There are also allot more XJS V12's out there. Same motor.
And don't forget... I've been wrong before.

 

I appreciate the input! While I do understand what you may be saying by how when boost comes in the whole attitude of the chamber changes, I also don't. This info is new to me, as in most things are, I'm 19.

 

Wish I had a XJ12 when I was 19.
The XJS forum will have allot more experienced impute.

 

Where did you find the info on the HE chambers poor acceptance of boost?

 

Here's the thread where we'll see if we can dig up info on boost and the he head. https://www.jaguarforums.com/forum/x...8/#post2212573

 

"Fettle the main caps!! Lest ye be facing the ragged edges of alloys split like pigs at slaughter!"
-Jack Sparrow

Welcome Ivan. Good to see you saving another XJ12, whether to be modded or not. I hear the V12 power can somehow be cranked up quite a bit. Though not for me, it would be impressive. Agreed that the V12 experts in XJS would fancy a good conversation.

 

I still have it, still in love, it's a current back up daily. Has plenty of power but always room for more. Raced a w202 c230 kompressor and smoked him. Wish we had more room so I can gap him. I literally scream and giggle when I race. Even when it's in my stock diesel chevette! I raced a vw bug and literally smoked him because I had to rev it out to 5k but gosh that's fun.