LT1 Swap: 1988 Jaguar XJS Convertible

When it comes to owning a Jaguar XJS of almost any era, the potential for an engine swap is never out of the picture entirely. From the heaps that litter used car lots, dragged there after years of deferred maintenance, to the sad cases of electrical fires that render the engine bay a smoldering mess. Fortunately, the fix for a needy V12 is well documented in the land of Jaguar ownership, with a few different V8 swaps possible thanks to enterprising owners. This 1988 Jaguar XJS is one of the early convertibles converted by Hess & Eisenhardt and features an LT1 conversion performed after the original 12-cylinder caught fire. Find it here on craigslist with an asking price of just $4,000. Thanks to Barn Finds reader Mitchell G. for the find. 

The seller confides he has way more money invested in this Jaguar than the selling price, to the tune of over $35,000. He claims the installation of the LT1 and repair of the fire damage cost around $19,000, and the XJS has also been repainted and had some minor rust repaired. The seller knows the car well, as it belonged to his father before he inherited it, who kept it garage-stored and presumably maintained to a decent standard to make it worth inheriting later on. The seller notes the original V12 caught fire not once but twice, and the second time was presumably past the point of reasonable repair. The LT1 installation looks quite tidy, like it belonged there all along.

The convertible models are generally less desirable from a pure performance standpoint, but the XJS conversion was done to a high enough level that the end result was one of the sexier drop-tops to come out of the 1980s, when convertible conversions were all the rage. The seller doesn’t mention any specifics about the roof or its condition, but given the level of detail shown elsewhere, it’s safe to assume it’s at least good enough to keep the inside dry. The seller notes some other maintenance items he’s addressed, including a new steering rack, new tires, new throttle cable and “…whatever else the car needed.”

The interior looks to be in fine shape, aside from some masking tape on the passenger side. The wood trim still carries a nice sheen to it, which usually isn’t possible when the wood has been exposed to the sun for years at a time or otherwise not maintained. The LT1 is hooked up to a rebuilt transmission, which presumably is still the factory unit. The seller says you can’t be a wallflower with this Jaguar as it attracts a fair amount of attention wherever it goes, and it likely makes a nice noise on start-up, too. The seller’s investment goes to show you that making improvements to cars that aren’t exactly world beaters on the desirability scales should be done because you love the car, and not in hopes of a new owner loving it even more.

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  1. Eric_13cars Eric_13cars Member

    Notice the top-down windows up approach to showing? And look at the console with the buttons all askew. Likely that the quarter window motors are not working. In my 90 (not an H&E convertible), there’s an electronic control unit under the package shelf along with 6 relays: Up and down for the top and quarter windows. When the top reaches a certain point in it’s going up and down, the control unit tells the quarter windows to raise or lower. Most of the time, the quarter motors themselves are operable but they overdrive themselves, the cause of them not working. On one of the forums, someone showed a technique using limit switches to prevent the overdriving (particularly in the down direction). I have some that I bought but have yet to install them. I’ve also thought about bypassing the controller and installing separate quarter window switches (I believe the earliest models of the XJS converts had separate switches…later on they became too smart by half). Also, this is the first I’m hearing about engine fires in the XJS V12. I have 75K miles on mine without issue. Maybe I’ve just been lucky. Frankly I’m not a fan of the V8 conversions in the XJS or XJ40. They’re stout engines when maintained properly. Most conversions I’ve seen are shite, as they say in the UK.

    • Mark

      The original V-12 css as ugh the fire not once, but twice

      That’s when I sprayed ice tea across the kitchen.

      • 370zpp

        Mark, you aren’t the only one who saw the “engine caught fire twice” as a deal breaker. If my motor caught fire even once I would be almost ready to sell or dispose. But twice? Sorry Dad, this needs to go.

  2. UK Paul 🇬🇧

    If engine fires were common I would have thought I would have read about it by now.
    First I have come across in 30 years of being a car but.

    • Husky

      Agree, I drive a 1994 XJS Convertible with the AJ 6 4,0 liter engine. Just talked to my mehcanicer Mr Roger Karlsson in Stockholm. He’s approaching his 80ts birthday, Been working with Jaguars since before the E-type/XKE was introduced in 1961. He never heard of a V12 engine fire either, but commented that if you are used to work on American lorry engines, it doesn’t qualify you to become a skilled Jaguar mechanic or the other way around.

      By the way, it’s possible to bore and stroke a Jaguar V12 to 10 liters displacement – wouldn’t that be fun?

      (I’m also a Mopar nut)

      • UK Paul 🇬🇧

        I really want a late convertible. Very envious!

      • Ross W. Lovell

        Greetings Husky,

        7.0 plus is the biggest I have seen.

    • Ross W. Lovell

      Greetings U.K. Paul,

      It was so bad that Jaguar had a “burn kit” package which consisted of the needed parts to put it right.

      Marelli ignition made it worse. Twin dizzys meant if you lost a coil at speed, the fuelstill poured into the cylinders but didn’t get burned. Eventually it would be pushed in the cat converter where it would light…….tada engine fire.

      You did hear of the later Nic-A-Sil and timing chain tensioner of the XK8 I hope?

      • UK Paul 🇬🇧

        Nikasil I have heard of. BMW had the same issue too.
        The fires though not come across. Interesting to know .. will keep an eye for any other references.

  3. ACB

    Unlike some, the Hess & Eisenhardt conversion of the XJS was done to a very high standard, the design as good as any factory convertible. I agree the Jaguar V12, maintained like any engine of the era, can be a robust and long-lasting unit; they’re a tight fit in both the XJ and XJS but they’re neither intricate nor complex (although the four-carb versions respond best to a practiced hand). The problem with the V12s was not inherent design flaws (al la the Triumph Stag V8) but slack quality control on Leyland production lines during the 1970s.

    Done well, XJs and XJSs with small block US V8s are good to drive. They’ll never have that turbine-like smoothness but the economics can be compelling.

  4. Frank

    These catch fire when you don’t maintain the rubber hoses between the fuel rail and injectors. But that’s not unique to an XJS, any car from the 80s with this style fuel rail needs to have those hoses inspected and replaced when they age out.

  5. Ed Stull

    The fire could be traced to something as simple as a jury rigged fuel line connector near a hot manifold. I attempted to save as much $$$ as possible on my ‘61 3.8 fixed head coupe, as opposed to the prices of the local dealership, but I never caused fires. And I don’t recall 12’s being known for that. However, only the owner can tell the story, and it’s hard to fault his honesty. I’ve loved the XJS convertible ever since I drove one a few times in LA. Even the sedan/coupe is a hell of an auto; the rumble of that V-12 is a car guy’s fantasy! The LT-1 conversion is a natural, and this one seems tidy. Bravo for a true Barn Find!

  6. Peter Bailey

    The Jaguar v12 is prone to engine fire due to fuel injection rubber hose on the fuel rail failure (ageand lack of maintenance) and fuel squirting onto the distributor and POOF!

    • Eric_13cars Eric_13cars Member

      Good to know, Peter. Thank you. I had purchased a complete set of hoses for my XJS but have not gotten around to installing all of them. I’ll take a close look at the hose to the injector as a result of your comment. Thanks again.

  7. tex cloud

    Wife and I have 1988 H&E XJS 18000 miles fuel fire didnt even burn wires or cap Ethanol ate fuel lines Fire Dept wouldnt pull bonnet latch pryed up with crowbarrs more damage than fire. Great auto!!!! Also have 1984 XJS I converted to 1995 Camaro LT1 15 years ago still going strong We belong to COJA :central Oklahoma Jaguar Association. Love the cats Tex & Diane

  8. Pat Gill

    rubber fuel lines, crowded hot engine bay, ethanol in the fuel, poor sense of smell, boom………….

  9. Claudio

    At 4 k i would buy it but i live in canada
    By the time it got to me , it would cost close to $8k
    And that would be too much

  10. Pat Gill

    A mate of mine turned up at my repair shop one day in his mothers car, asked me what the smell was! I gave him a couple of feet of fuel line, a couple of weeks later I collected the car for an insurance inspection after it had caught fire and was badly burnt, just before the engineer turned up to assess the damage (total loss) I removed the coil of fuel line from the passenger seat, the only part of the front of the car that had not burnt……

  11. gary kline

    Car is a blast to drive! I just ordered new tires! Thanks Barnfinds!

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