I finally bought another XJS. I loved having one of these in college, and it is still gorgeous. I bought this one with 74,000 miles on it:












However, after owning it for one day, it suddenly overheated insanely fast and blew a rod. I choose to take the original owners word for that it was running well when he sold it, and it did run well for me for one day.

I am sad and confused. The car is still gorgeous, but it is simply a 5000 pound paperweight right now. I figure at this point I'm in for a penny, in for a pound, and I am going to do a Chevy 350 conversion to it. I would have much preferred a stock V12 car, but I am where I am right now. I know many will consider it sacrilege, but I have no choice.

Expect many, many questions from me at a go through the conversion process. Hopefully a few here have done one.

My initial thoughts are this:

a John's Conversion Kit: Link
a 500hp fuel injected 6.0 liter Chevy engine: Link

My local shop has done a couple of these already and seem very comfortable with the idea. I found them on this forum. It is Ronnie at Tel Aviv Texaco in Miami.

Any input at this point would be appreciated.

 

Looks like a very nice car! Sorry to hear the V12 expired.
If you're set on a V8 conversion, in my opinion, an all aluminum, fuel injected LS engine and corresponding overdrive transmission or 6 speed would be a better choice, over a iron small block, albeit more expensive.
Nothing against John's Cars, in fact I've used one of his kits on a Triumph (very well done) but he does not offer a kit for the LS based engines.
However, Andrew at Jaguar Specialties does offer a LS kit, as well as the small block.

Jaguar Specialties

If you decide to stay V12, perhaps some members here could offer some advice on where to source a used one.

 

Go for it it will probably the best thing you do��

 

By the time you buy the kit, pay for the install and its hassles you could have sourced a V-12 and been done and for less $$. V-12 coupes in FL go for pretty cheap as it is.

 

I would love to go all aluminum, but it might be price prohibitive. The engine manufacturer in that listing also offer aluminum blocks, and I will find out tomorrow how much the upgrade it, but I expect to be sitting when they tell me the price.

I expect to spend about $2000 on the conversion kit, about $2000 in labor, and about $8000 on an engine. That puts me at about $12,000 for the whole project, plus maybe a few hundred more for a refresh of items that cannot be reused in the new build.

I was going to use the exiting T400 trans with an adapter from John's.

I don't want to go with a used V12. I am still paying a fortune to swap it out, and I am worried about future problems down the road with it. Not to mention the lack of power.

 

Thanks. I am a bit stressed about putting $12k into a car that will be worth far less, but I doubt I will ever sell this car anyway.

 

Never mind all this bollocks stick a decent v8 in it and have a car that will be reliable and not over engineered

 

I always hate to see a V12 replaced by a Chevy V8, but, I agree with Greencar89, that if you're set to do it, you really should go with an LS. Heck, if you expect to spend $8k on a motor, you can likely get a good used LSX with all the wiring & computers you need to put it in the Jag.
Also, you should consider parting out the the V12, and other things you pull off, in order to help pay for the conversion.

 

Its a good looking car but you don't need to rush. Do it cheap, do it twice.

 

Thanks for the guidance. I will look for a used one and check out the price.

What parts on the V12 are worth parting out and what is a ballpark value? I would rather sell the thing whole for anything over scrap value and not deal with that though.

 

Here in Aus we can buy an LS3 crate motor for $8KAUD surely you can get one cheaper in the USA

 

when you get it done bring it up to Jax, I'll show you my v-12 coupe with a "lack of power" ps, my slow v-12 in impeccable condition is for sale for $5500, a far cry from 12k for a Jaguar with a Chevy transplant which won't sell for a fraction of 12k. Your money, your car....but you did ask for advise. Plus to spend all that money and keep the 3speed trans???? I seriously must be missing something. Plus why even go after a Jaguar v-12 if it suffers from "lack of power". WAY cheaper to go v-12, John's cars quarter breed kit and a different rear ratio.

 

mines plenty reliable, for the past 8 years of ownership. I think a distributor cap had me duffed at one point, hardly "unreliable"

 

They are British reliable. The car could handle much more power, chuck out the v12 put in a v8 get the sound and the easy dist cap change

 

Jeez, I didn't mean to offend anyone.

I drove an '88 V12 XJS for years in college. Yes, it has power, but it is heavy car and was never as quick off the line as I liked. I certainly went from 30 to 60 pretty quickly, but 0 to 30 was lackluster IMHO.

Out of curiosity, how much do you think a V12 swap out would cost? Installation will like still be $2000, but I would save the $2000 conversion kit. It really depends on what I can get a rebuilt V12 for. I would not want to put even a low mileage used V12 in there without rebuilding it while it is out of the engine bay.

 

Yes, the one I linked is an LSX for $8k; it just is an iron block instead of an aluminum one: 6 0L 500HP High Output Resto Mod Trans Am SUV Tahoe Truck LS1 LS3 Reman Rebuilt | eBay

It is also turnkey to save a bit of installation costs on installing the accessories. As a crate engine I am sure it would be about $1000 less.

The question is whether it will be worth it to go all aluminum.

 

You're stressed about $12,000 just for the engine swap (Gah! I certainly would be!) but seem intent on going with the most expensive choices. V8 conversions can be done for a lot less money with a good result.

Or for less than half that amount just buy a different (but very very nice) XJS....such as JT's.....and sell this one for whatever you can get. Cut your losses!

Cheers
DD

 

There are lots of shops out there that specialize in LS engine/tranny combos. I bought and LS1/4L60E with 88k miles combo for $3k. Most lower mileage ones will go for $6-8k, tranny included, and there is no reason to keep the TH400.

You can find a variety of LS motors that fit the bill, from the GTO, -2002 Camaro/Trans Am, various truck motors, or newer Camaros 2010+. I was seriously considering the 6L80E tranny, which would make your off-the-line performance brilliant, with economy to boot.

And I don't know... if the engine threw a rod the day after buying it, I just wouldn't accept "Gosh, it was running yesterday" as an excuse. Something is out of whack here, especially if you paid a premium for a relatively low mile V12.

And be careful buying those V12s, I've investigated several on eBay, and there are some out there that are not as they seem.

Oh by the way, I have a 1990 V12 with 77k miles. Still in the car, no idea if it runs, but you're welcome to try...

Padre

 

how is changing the dist cap on a v-12 hard? "British reliable" not sure what that is, my Jaguars are every bit as reliable as any other make I've owned, you may want to step up your PM if your British cars are unreliable.

 

Thanks for the offer Padre, but I am sold on the conversion.

And yes, I choose to believe it. In any reality I know of, a car doesn't throw a rod the day after you buy it. But it is not like he is going to give me a refund or anything.

I am warming up to the idea of an LS3. A brand new crate 480hp LS3 from GM is not as expensive as i thought ($6490):

GM Performance LS3 376 6 2L Gen IV 480 HP Engine 19301358 New Chevy Crate | eBay

But I will need a controller ($1177):

19259261 GM Performance LS376/525 Engine Controller Kit at GM Performance Motor & Parts

and a tranny ($1695):

4L60E 4L65E 4L70E L 3 2WD 4x4 4 3 4 8 5 0 5 3 5 7 6 0 6 2 HD Chevy Transmission | eBay

Grand total of $9362, plus the conversion kit and installation. It definitely adds up...