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Thread: Jaguar V12 HE Transplant

  1. #1
    Junior Member
    Join Date
    Jun 2007

    Jaguar V12 HE Transplant


    I have a Prova Lamboghini Countach kit which has a Jagaur V12 with four SU Hif6 carbs. I have had the car for some time but never on the road and just got it started the other week. The engine wasn't running that great and was leaking oil, water petrol, etc, so instead of spending any more money on it i bought a Jaguar XJS V12 HE. The idea is to lift the engine, wiring loom, ECU, fuel pump out and drop it in the lambo. Just wondering if anyone had lifted everything out of an XJS and got it to run in another car and what things i need to look out for and any problems people have had.

    Thanks for advise.


  2. #2

    Re: Jaguar V12 HE Transplant


    That's a huge job but not impossible. If you don't already have it. Search for Kirby Palm's book (Free Download). Experience In a Book is the title.

    I've owned 4 XJ-S cars and still own a 1991 XJ-S V-12. I suggest that if you are using a jag V-12, that you select a donor car above 1990 where there is a bit of a chance that you will have less electrical issues.

    You'll need a heavy duty engine hoist as the engine and transmission together is a lot of weight. Kirby's book will give you all of the in's and out's of removing the engine. NOt exactly a fun job but not too bad.

    Don't get me wrong, I love my 1991 XJ-S. Most of the electrical nightmares have been worked out and the car runs like a bear.

    However, keep in mind (especially in a Lambo replica) that the V-12 is a hot running engine, you can not overheat these engines. You will drop valve seats into the cylinder if the engine is overheated. The Jag uses a 1-1/2 pass radiator which is a very poor design. One bank runs quite a bit cooler than the other and this is where the temp sensor is located.

    If the guage in the Jag you are looking at goes above the "N" (past the mid point of the N on the gauge actually), The car is running too hot. Stay away.

    I love the cars. They take a special touch but even with that, I wouldn't want to use the engine in a replica. Mine is the larger 6.0 liter (not the usual 5.3 liter).

    Not exactly brimming with horsepower, the 1990 5.3 liter is about 262HP. (I'm more than happy with the 6.0 liter that I retro'd into my car. Slightly modified, the stock 313HP was ok but still not exactly "blistering performance" . Although the cars are not designed for off the line performance. I'm now at about 335HP and when I actually get around to removing the restrictive exhaust, I should gain appx 20 or so more conservatively. Just enough for the car).

    Hope that get's you started.

    Where are you located by the way? I'm in PA. Your more than welcome to stop out and see my V-12 if you need to.
    Previous Builds: AF - 308 Replica w/ V8 & GM F-body Testarossa Replica
    Current Toys: 308 V8 Project #2, 91 V-12 Jaguar XJ-S Coupe. 1983 Hurst\Olds, 1979 Trans/AM - 468CID Bracket Car.

  3. #3
    Junior Member
    Join Date
    Jun 2007

    Re: Jaguar V12 HE Transplant

    Yeah is going to be a big job, but hopefully worth it when its done. I have already got my donar car its a 88 XJS. Am going to run the car for a few months first just to make sure the engine is strong and with no problems before i remove it.
    Other than boring out the block is there any parts or things i can do to get the power up? cams, pistons, con rods fueling chips and anything like that. I am finding it difficult to source any performance parts or modifications. Download that hand book so I will go through it, although it might take me a while there is few hundred pages...Thanks for the advice.

    Am in Aberdeen, Scotland, UK so it wont be possible for me to come round but thanks for the invite.

  4. #4

    Re: Jaguar V12 HE Transplant

    You're correct. Not much in the way of performance items for the V-12. Boring the block is a real chore. Possibly since you are not in the U.S. you may be a bit luckier to find someone that can give you some ideas for mods. I think there are a bit more enthusiasts "over there" and a bit more knowledge about the cars as well.

    The blocks use sleeves which I believe can not be bored. You can however (I think) remove the sleeves, modify the bock and re-sleeve the block to a 6.0 which is essentially what my car uses. You should also have the older Ignition System with your car. I have the Marelli which has to be modded to prevent those "pesky" engine fires that the Jag's are known for. Cheap mod found in "the book".

    There are however cams available for both the 5.3 and the 6.0. I'm more than happy with mine the way it is. After the exhaust, I should be approaching the 360HP mark which is just fine with me since I only put about 300 miles a year on the car. I just like the body style. My wife's 3000GT can smoke the jag in the 1/4 mile.

    (However the Jag tops out at about 190mph so once I leave her in the dust, I'm nowhere to be found .... Of course , I'm also 2 states away by that time...). also, the Jag's brakes being "marginal" are not the best for stopping the heavy car. I've only touched the 140mph mark and that's about all I'm will to do in the car. You won't have to worry about that.

    On your 88, pay particular attention to the Ignition Amplifier located on the intake (I would suggest relocating it during the swap since it gets very hot on the intake and causes problems). Also found in the book, you'll find out that you can update / repair / convert the Ignition Amp with a mid 70's HEI module (which I did on my 1987 and 1986).

    Also be sure to check that both thermostats are in the engine. Some people try to remove them when they run hot (which can actually make them run hotter). Jag V-12's need both of their thermostats installed.

    Everything you need to know about the V-12 is in "The Book". I actually printed and bound mine. (Took me about 3 hours to print copies over the course of a few days at work. Much easier to read than on the computer screen.

    Last... Join the Jag-Lovers forum. Lots of great info and Kirby Palm still frequents the board. Good source for performance info, general info etc.

    Previous Builds: AF - 308 Replica w/ V8 & GM F-body Testarossa Replica
    Current Toys: 308 V8 Project #2, 91 V-12 Jaguar XJ-S Coupe. 1983 Hurst\Olds, 1979 Trans/AM - 468CID Bracket Car.

  5. #5
    Senior Member
    Join Date
    May 2002
    Los Angeles

    Re: Jaguar V12 HE Transplant

    If you insist on using a Jag engine, you'd be a ZILLIION times better off using a 1995 or 96 Six cylinder - THAT engine is terrific and would last a looooong, looooong time if properly maintained.

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