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Hey there! I've wanted an XJS coupe for the longest time and it looks like I might finally be in a position to make that a reality. I've found one about 200 miles from me that seems like a great deal, I've read the buyer's guide, but I wanted to get the opinions of you folks first, as you all obviously have much more experience with these than me. The car is priced at $4k, it has a Chevrolet 350 mated to a 400 auto, the car itself has about 25k on it and the drivetrain has less than 1000 miles. The owner did state that the car sat for a long time prior to the installation of the new Engine/Trans. It's a western car, so there's little to no rust, the original black paint is still good and the interior is immaculate. the gauges still need to be reconnected, but according to the owner everything works, including the A/C. The new owner bought it from the man who did the 350 version with the intent to pull the engine, but never got around to it.
So here are my questions:
1). Are there any particular problem spots to look for on cars that have previously sat?
2). Does anyone on here have a 350 conversion? How's the gas mileage with this car/engine combination?
3). How difficult is it to connect the Gauges?
4). Is there anything I should be asking the seller that I'm missing?
5). Is there any other advice you folks can give me?
Welcome to the forum and I hope we can help you to find your first XJS.
Be aware that the car you are looking at has an issue that will open a big can of worms. That being the Chevy engine.
In your position of looking for your first XJS I think you would be missing the true experience of the XJS if you don't have the original V12 engine.
You will see many folks debate that the Chevy engine is more reliable, easier and cheaper to repair and gets better fuel mileage. All of those things might be true but in my opinion you are no longer driving a Jaguar XJS as it was meant to be.
For $4000 you could find an XJS in equal condition to the one you are looking at but still has its original V12.
Some feel that the Chevy conversion does not affect the vaule of the car. My opinion is that the value is reduced with the conversion and I would never consider such a car if future value was a concern.
I would also be concerned of the quality of the conversion. Do you know who did the work? Was everything done properly? Do you know how to the inspect the car to make sure it will be safe and reliable?
If you really want the true XJS experience then I would suggest that you find the best V12 car that you can afford.
Unfortunately you will probably get a lot of responses that will chastise you for even considering a Jag with a Chevy engine, but I am not one of those people. There are arguments over V12s vs I6s, growlers, leapers, tail lights, it can get quite heated sometimes, so try to ignore those comments. If a Chevy engine works for you, then go ahead and do it.
I'm assuming the AC works?
Radio?
Cruise Control?
Cars that sit for awhile may have issues with gaskets and seals as well.
I would have to tell you that unless you are really into cars, I'd shy away from any kind of customization like this. It's really hard to gauge what was done and what wasn't, and then what was done correctly. I would worry that a garage wouldn't even know where to start because there's no handbook or manual for them to follow.
If you have your heart set on a Jag with a Chevy engine, I would find one that works...all of it. It really won't be too hard. I do believe the resale market on those conversions is not very strong.
At least with the v12s, the problems are known and the parts are easily identifiable. With your car, you won't know until someone tells you.
To me theres a huge red flag with the fact that the gauges aren't hooked up. If it were something easy to do, it would be done. I would bet that the there's a steep learning curve with getting those gauges to work.
I have an 86 XJS with 350 conversion. I love it. I've had 2 V12 cars and I prefer the sbc. Not to **** off the purists. I think the v12 is an underperformer. ( yes I said it ) my small block has more hp and torque. Parts are readily available for the sbc. Not so much for the v12. Yes the v12 runs smoother but in a 3600lb car I want more power than most of you.
The gauges shouldn't be to much trouble. A bit of messing around.
I believe that a converted XJS is the best of both worlds. sbc performance and a great ride.
I will get another v12 car someday, it will have to be perfect.
Email me at jamiethedentalguy@gmail.com and we can chat.
There are many really, really poor conversions out there and one of the biggest things you need to contend with (plan for is a better term) is emissions.
If you are in an active emissions area (for 1986 cars) with a sbc converted xjs running a four barrel carb, you could be in a position whereby it cannot pass smoke. The rule is generally no engine older than the car you're converting, but being that the xjs was fuel injected from the start, a carb fed sbc could be an issue.
I've known a few guys that ran into this issue.
Aside from that, it's plain, ancient unbreakable technology, with infinite tuning and power capabilities.
I personally think sbc lumps have run their course, and appreciate thinking out of the box options better (i.e later Jaguar v8's, etc.).
Not sure if folks have priced a V12 rebuild lately, but a fully farmed out job is Porsche 911 territory now, with $20k not being an absurd number, so I get it, options are good.
The problem I have with the conversions is the quality. As each conversion is individual, it can be impossible to know how well it was done. I've heard of some horror stories where a backyard mechanic used the same colour wire for everything. Good luck tracking down a problem, because you'll be on your own.
A chevy motor can make more power, but if it was a plane jane emission engine from a mid 80's Caprice you're trading a 260hp V12 for a 180 hp V8. Not a good trade in my books.
One of the most common failure points on a V12 is the GM ignition module, exactly identical to what is used in most 350's, so I'm not really seeing an advantage of changing motors and using the same failure prone component.
Thank you all so much for the feedback. I'm very nervous about buying a jag of this vintage in general and the advice is reassuring. I'm not that worried about not getting the pure XJS experience, because I'm 100% certain that this won't be my last XJS and the only other coupe I can find for sale within a 300 mile radius is absolutely trashed. All the other ones are convertibles, which is absolutely not an option, as I study car design in Detroit during the winter. The car currently runs, quite well according to the owner, it was a new crate engine, and the 350 is outfitted with some high ticket Edlebrock parts, which make me think that the PO probably knew what he was doing. Future value isn't really a concern, as I have no intention of selling it anytime soon if I end up getting it. According to the owner all electronic components work, and the brakes are in good order. I didn't even think of the emissions thing, but luckily neither of the states I live in require it. I'm not married to the idea of a 350, I don't hate it either, but it's more about availability. Since the engine and transmission are fresh and haven't sat, is there anything else specific that I should be worried about?
Firstly couldn't care less what drives your car, that’s up to you and what you like.
Now I'm sure you have done a little home work and looked at certain things before you exchange dollars. Rust is the big killer, lift the carpets in the floor pan area and in the boot (trunk to the Northern People) under the underlay and right down till you hit steel. Check what’s there, the floor pans there have rubber strips glued down look below them. Top of the boot around the sills and the back guards are another bad area.
Some other things like front wishbone bushes, ball joints and steering arms and bushes, all are a ******* to replace on the car.
For the record I’m a V12 fan and believe in advancing the original more than replacing, my 2c worth is ditch the SMC and find a really good LS motor. To go back to a v12 will cost you 4x what its worth, if you want a V12 find a working one plenty of them out there.
To my way of thinking, whether a V12 is more valuable in terms of money than a car converted to V8 is without meaning. an investment, they are not. Pleasure, no question.
But, a skillfully done swap beats a messed up original hands down. Conversely, a good and well maintained original beats a junky swap.
Most monkeys can clamp on an after market intake and carb to an SBC. Makes it better, mebbe so, mebbe not.
But, yeah, the jurisdiction and the SMOG issues are of great import.
Some time ago, and somewhere else, I read the story of a fellow that bought a nice XJS with a distressed V12 from an equally distressed owner. The buyer swapped in
an SBC. Lo and behold the original guy bought it back and was pleased as punch.
In about 2001, I bought a very nice 83 XJ6. It looed great and ran great. Power not up to my usual, but, good enough. Not too long after, I went on a business trip to nearby, sorta, Stockton. AC doing great in the summer hear. Power for the Altamont pass adequate. First stop, just fine. Did task at second stop and ready to go home.
On I5. Wowee, temp goes way up, smokes out the pipes, growling noise, engine
quits!!! Coasted off the freeway into a gas station. No run, ever again. Went home on a flat bed. 0 compression in all holes. Done for.
It's a western car, in the same area you can find rust free Chevy Vegas. You guys are scaring me though, if I end up getting the car are there any model specific precautions I can take to make sure it stays that way during Detroit winters?
Carl, did you do your conversion yourself? What engine did you use?
Yes. the biggest thing I ever did. Including a "hot rod of the 40's" from scratch and junk!!
I bought a package from a California "'recycler". Donor car was a 94 Cadillac Fleetwood Brougham. One of the varieties of the LT1. 4L60E transmission.
An install kit from Johns cars in Fort Worth, Texas. And a wire harness from a now out of business vendor. The former just fine, the latter not so much.But, no need to name as he is gone.
Lots of power. Good mileage. Very smooth. Up until now, very reliable. Glitch in charge. Could happen anytime to a 31 year old car.
But, a definite enjoyment in getting it done and running and past SMOG. Tons of fun to drive. The OD transmission alone s a huge improvement.
Do it, you will like it.
Caveat, if a decent job was done.
I'd hesitate as to a carb'd engine with only a three speed auto. EFI and Od, so much superior.
From your previous post it sounds like you prefer a Coupe and don't mind the Chevy motor.
I think $4000 is a bit high. If you can get into the low $3000 range then it might be worth it. You will most likely spend a few thousand the fix the gauges and complete any part of the conversion left un-done.
In case you were not aware John's Cars offer engine conversion kits. You should talk to him as I'm sure he could help you to figure out what parts you need to make the gauges work.
You said the XJS you are looking at has only 25,000 miles on it. If so I would expect the body and interior to be in excellent condition. You should have very little that needs repair or replacing.
Makes me wonder, with such low miles, what happened to the original engine?
It does make you wonder.
My 86 was converted in 91. Between 86-91 there was $8600 worth of work done. 91 an estimate for $6800. PO declined repair and did sbc swap for $8100. All repair bills after that were $150-400. Tune up, brakes and so on.
How can a five year old engine have so much in repairs. There is something wrong with its design.
This swap paid for its self ten times over.
UPDATE: Got the seller to shoot me a few more pics from under the hood. Apparently only the Oil and Temp gauges are disconnected and the PO wired up some aftermarket ones under the hood that could be moved to the interior. Is that a red flag? I'd be okay with aftermarket gauges. The current owner is asking 3,000 for the car with the drivetrain, or the complete car for 4,000. I'll definitely try and knock it down a bit if I go this route. I'm actually kinda hoping it was a Johns Car kit used in the conversion, I may call them tomorrow to ask if there is some way to identify the make of the kit used. The current owner doesn't know why the swap was done, I'm kinda guessing that the PO decided it would be easier than getting the V12 running again after the car sat.
What's to wonder? Almost certainly there was a cooling problem of some sort that was either unnoticed, or noticed but ignored, or noticed and not correctly repaired. That's what kills almost all of the V12s
There is something wrong with its design.
It's a weird design, and unforgiving, in terms of the cooling system. Knowledge of how it works is the most important thing......and what's most commonly lacking.
How are your mechanical skills? Do you have a garage, tools and time to work?
If you have to rely on other mechanics to to do the work then this can get very expensive very quickly.
Even an unmodified XJS can be expensive to maintain. That's one of the reasons that the prices of these cars is so low. It's too expensive to have a shop do the work so most average people wont buy one. Most of us owners do our own work.
If you have the knowledge and skills to do the work then this car might be ok for you.
Otherwise, without knowing more about the conversion and the quality of the work a car like this is a big gamble. Be careful.
Doesn't really look like a very sanitary conversion, IMHO. At least not in terms of the detail stuff.
You're more polite than me Doug! It looks like a hack job to me. A shroud is critical to having a fan work efficiently, no doubt that's why the electric was added in an attempt to cool it off. A temp gauge under the hood doesn't do much good when driving!
Some of that wiring looks pretty nasty too. I've found crimp joints are nothing but trouble.
You're more polite than me Doug! It looks like a hack job to me. A shroud is critical to having a fan work efficiently, no doubt that's why the electric was added in an attempt to cool it off. A temp gauge under the hood doesn't do much good when driving! Some of that wiring looks pretty nasty too. I've found crimp joints are nothing but trouble.
You guys are all nicer then me...what a pile of s-£€t, Crate engine? With Rams horn manifolds? Clutch fan with electric fan? Mechanical fuel pump on a crate 350? $4000? run don't walk away from that thing. That thing came out of a crate all right with 1965 stamped on the side of it.🙈🙊🙉
I agree that it needs to be cleaned up. The clutch fan without a shroud and the single electric fan. Needs shroud and remove electric or remove clutch fan and add twin electric fans. Wiring and hoses need cleaning up.
I have a set of mechanical gauges where trip computer was. The original gauges still work but aren't as accurate as my mech set.
The motor mounts look the same as mine. Don't know who supplied them, they've lasted 24 years.
Its just a small block Chevy
06-10-2015, 10:57 AM
1986 XJS 350, Good buy?
