How many people on here have blown their engines? The V12 is a fully forged beast. Shoving a different engine in it is "fixing" one of the most bulletproof bits on the whole car.

 

So you drove the car for an entire decade and are frustrated that it now has a problem?

You have and idle issue and you are frustrated because you threw parts at the car. It is always frustrating to guess, blow money, and the be wrong. What are the injectors doing? How is compression? Are the O2s good? You can simply swap coils around or check their resistance with an ohmmeter, that isn't the car being shitty, it isn't a reason to lump the entire engine, it is just you hoping and buying, of course that is frustrating.

 

The oily bits may be forged, but the reason many owners give up on the V12 has nothing to do that fact.

The most common v12 failures are related to dropped valve seats and failed head gaskets. Both require head removal which can be unusually difficult and relatively expensive when compared to other engines.

Thus the decision point, expensive internal engine repairs followed by possibly another failure or be done with the risks and lump. It's an individual decision.

 

I can't imagine ever wanting to lump any vehicle I remotely cared about.

Cars are designed and assembled in industrial car manufacturing facilities, the likes no mechanic or individual has access to. Designs, tolerances, fittings , and almost every detail is tested in ways that most lay people can't . I can't even begin to imagine how a car with a different engined shoehorned in by some shop, or worse, in someone's garage, suddenly becomes more reliable than a design that probably 100's of different automotive engineers designed and tested. The whole concepts does not make any sense in any way to me. All of a sudden you basically have a homemade car that's been made to work with the cars original ancillaries.

Also, I have never heard of someone wanting to lump a AJ16 car. Ever. It makes me think this whole thread is a joke, and if it's not and one is unable to deal with a AJ16, then a 20 y.o Jaguar is definately not the car for you.

 

The sbc is probably one of the most iconic engines built. There's a reason that these engine are able to produce 500 hp unlike the V12

 

Whot mate?

These are the most common critical engine failures, but they are not by any means "common."

Run through pages and pages of this forum, it is all everything but the engine that people have issues with in this car. I have overheated the **** out of mine without a valve issue, that issue is rare. Head gasket issues are nearly unheard of. Not a clue what you are on about or where you heard it from.

 

You are right, the TWR Jag only made 750hp, which is less than 500hp, right?

Also, bigger brakes are better, plastic gas tanks don't rust out like steel, 2 seats are inconvenient, R12 isnt available anymore, direct-injection is more efficient, outboard brakes are easier to work on, LED headlights are more effective ETC.

You switched to an SBC because obviously the stock engine capable of 160mph was just a piece of junk, you only want the best, that is why your XJS is basically on par with a 2016 mercedes, errr impala, in terms of technology, right?

I never understand why that is the angle you guys take. Why can't you just say you were afraid of it breaking and not being able to fix it, that it had some other problem you couldn't fix, or that you just bought the car with a swapped engine because it was cheaper? No, it always has to be, "my car has a v8 because it is better than yours." Who cares? My bike is faster than your car and cost less than it too, but is that a reason to crap all over it?

The XJS isn't a sports car, it is a tourer. It outpaces most of the cars made in its time and still passes perfectly fine as a GT car today. You can find faster cars for less money and you can find slower cars that are more fun to drive. The XJS is a package, feel free to customize it to your hearts content, I just don't see the point in dumping on everyone else when none of them bought an XJS because it was fast, they bought it because they liked the sum of its parts.

No matter how fast your car is, there is always going to be someone out there with a faster one, so stop stressing about how fast your car is and just enjoy it. If you have never driven an original mini, please do yourself the favor.

 

Right on the money! As for dropped seats, that's a direct cause of an overheated engine, which if we're splitting hairs means the car wasn't taken care of, save and except a complete loss of coolant on the highway or the like. Everyone needs to remember the car was never a Camry when new (thank God), and attempting to make said jelly bean via lumping compromises the overall package. Seriously, go buy a ZR-1, you'll be happier and you won't have to hear from us originality snobs that actually believe the V12 is a great power plant and requires no more special fetting then a SBC if properly taken care of. Like any car, if you live on a shoe string for maintenance, you bet it will bite you.

Cheers.

Jeff

 

My 2 cents--- Take out the V12 and it is no longer a JAG.
If you do take the V12 out be sure to remove the V12 badge and replace with 350, 454, etc. and take the JAGUAR badge off and replace with GM or CHEVROLET badge.

Mine has a heat issue, AC leaks, rear right window does not work, antenna does not go down, right front speaker goes on and off, drips oil, fluid leaking from somewhere when raising, lowering the convertible top,I turned lever to manual, if you punch accelerator to the floor it will stick in low gear till it cools off so I just accelerate to the notch and not beyond and runs fine. I still LOVE my JAG and with help from members (WE WILL FIX EVERYTHING).
Still a happy camper. 1990 XJS V12 convertible BLACK / CHROME.

 

question; why do we NOT have any LS series engines in XJS?

great engine , really better than old version of SBC.

 

Except in production cars (eg Caprice) throughout the 80's (comparable time frame to the HE V12) the 305/350 was putting out somewhere between 140-185HP, depending on the year.

In full emission trim the 262HP (Euro spec 300HP) V12 looks very good in comparison. Sure, a worked over 350 can produce more, but it's not exactly fair to compare a modified SBC to a stock V12.

The V12 is an iconic engine too for that matter! The only true mass production V12, since I don't count Ferrari's as mass production cars.

There can be many reasons to put a different engine in a Jaguar, but increased reliability of the whole package of car + engine isn't one of them.

 

To each his own!!! No question about it, right or wrong???


The SBC in my XJ wuzza six is the latest version of the iron block
engines, the, LT1 In my car tuned for torque to move the big 94 Cadillac that donated it. HP modestly rated at 260 HP. torque well over 300. And relatively low in the RPM's.


The Jaguar V12 and DOHC 6's are magnificent engines.


It is in the more advanced management systems and OD of the GM
ABC's that make the improvement.


Oh, lighter and smaller as well. Take up much less space in the engine bay. So, less ambient heat to cook components.


PCM managed dual Efans, a bonus.


Alloy AC compressors????


Swapping plugs and plug wires in my SBC no picnic, but
compared to a V12 !!!


Concede, plugs and wires in the 4.2 a walk in the park. Slick.


When my car was 4.2 powered, I loved it. Adequet power. Decent
gas mileage. 2.88 in lieu of OD acceptable. Intriguing, no question.


But, as now powered, wow!!! Smooth, peppy, faster than I'll ever drove it... Great fuel mileage.


Carl

 

Because most people with SBC XJSs bought them like that,didn't have much to speond, or installed them because they can't work on anything more complicated than a rock and 2 sticks. Installing a modern engine with electronic wizardy doesn't fix the lack of know-how.

Though there is a new video on the smoking tire of an XJ8 with an LS3 in it.

 

A stock XJR6 will smoke the tires.

 

Or the 82 Ford Fairmont with an LS1 and large turbo.

 

Lumping it is like a boob job...eventually someone is going to ask you to lift the bonnet, and how are you going to feel then???

Whatever is "wrong" with it can be fixed, and certainly for less than an engine swap.

You ask for opinions, but it's your decision...

John
1987 XJ-S V12

 

[QUOTE=J_C_R;1434354]Lumping it is like a boob job...eventually someone is going to ask you to lift the bonnet, and how are you going to feel then???

John,

not sure this is the best comparison as a good boob job is often a nice improvement and can make opening the bonnet as you put it a worthwhile exercise or so I have heard-LOL.