OK I took out the "Period." Of course it's subjective.

 

hope you guys dont jump on me!
if it wasnt for GM my car would never have seen the light of day!
lottsa ,lottsa , GM parts on my 1978 XJS V12!
ron

 

The automatic transmission is so slushy with a V12 that they mute most of the qualities that make a V12 special.

I have the luxury of being able to drive a Jag V12 with a T56 back to back with an LS engine car with the same T56. No comparison. LS is way faster but the V12 has some qualities that are really unique but more subjective and really shine through with a manual transmission.

For example...
Nice relaxing even tone, when uncorked too.

Smoothness and torque at very low RPM's (300) makes it seem like you are always in the right gear even for passing.

General ease of driving, difficult to stall a v12 if you are leas than perfect with the 3rd pedal.

Very few harmonics are transfered from the shifter to your hand. You can leave your hand on the shifter all day and drive without any fatigue.

 

Still spewing this incorrect info huh? Not all small block Chevy engines are made equally, they came with a wide range of specs and factory setups. To equate all small block Chevy engines to your often mentioned "160hp" version is severely misleading. Additionally, you purposely choose to leave out the gen III and IV Chevy small block engines because they're ODB2. Because, if you included them, then your entire dependence on referencing "160hp" small block Chevy's would go to ****. Lets be honest, the cost of admission for gen III-IV engines isn't significantly more than the small block of the old days. Now, here's the real kicker, swapping in a more modern (OBD2) Jag engine would be significantly harder than a Chevy LS. They're bigger, more complex, and do not make as much power. Even the supercharged AJ's, with their near 400hp, aren't as efficient at making power as a LQ9 6.0 Chevy making the same power. The AJ will heat soak after a few runs and be down on power. And the supercharger and A2W intercooler system adds even more weight and complexity to the swap. I'm speaking from experience as I own a Jaguar XJR and though I love it, its drawbacks are hard to ignore. The HVAC interface and gauge cluster is easier to solve than anything AJ related regarding to wiring.

Why don't you simply justify your distain for Chevy V8 swaps by simply saying you don't like Lumps. Instead of using picky-rather-false information to deter folks from lumping their Jag like multiple other posters in this thread? That makes sense; simply not liking something a certain way. I would never Chevy V8 swap a Porsche 911 (unless I got it as a salvage roller and I just wanted a balanced racecar) but I would surely and plan to Chevy V8 swap my V12 XJS. Imagine telling people who like pineapple on their pizza to refrain from such violation of pizza because of some made-up pineapple facts that you halfway made up. LMAO!

P.S.
Please don't reply with your typical lesson on SAE vs DIN and all that jazz, because at the end of the day, its their car and their money. No amount of lies, random mis-information and purposeful omissions will change that. You have been a broken record for years on more than just this forum.

 

I bet that's a smooth driving experience. V12's with manual transmissions behind them is certainly a dynamic that you cant easily replicate using any other combination. Imagine a Jag V12 with a transmission that's actually smoother than the T56!

 

Piru another almost unkown about the V12 with manual trans factory 4speed, i had a 1975 XJ12 coupe!
and an old Jag mechanic said some thing to try, for fun!
car running fine pull over on deserted road, shut engine off, put car in 4th gear clutch out, no feet on any pedals , turn ignition key on start, car just pulled away smoothly, NO bucking or shaking!
all the way to 90mph, without touching the shift lever!

knockoff mounted wire wheels, NO lug nuts!

manual shift 1975,, how this for useless information!

 

I want! LoL

 

There is indeed some disconnect here. My 87 XJ6 was converted to an LS1 from a 94 Caprice Interceptor [9C1] which put out 260 hp and 330 lbs of torque mated to the wonderful 4L60E tranny. This conversion was relatively trouble free even here in California where the smog refs can be quite clueless [initially refusing to honor the TSB approving the deletion of the smog pump]. The V12 was slightly smoother, but the LS1 is far more economical, quieter throughout the rev range and vastly easier to work on. Aftermarket upgrades are more readily available and far less expensive.
While I certainly understand the skepticism of the purist, from the driver's perspective the "lumped" car is, hands-down, superior.
You might take a look at the video series. Wonderful teaser on how to build an XJS using a suburban motor [I love that vortec fi truck motor. Built one for my Bayliner]

Project XJS-LS (Parts 1-14)

 

The simple truth is most lumped cars deserve their reputation. A modern LS conversion will out perform a 4.2 Jaguar six cylinder engine which was designed during WW2 and remained in production through 1987.
At a cost. A professionally done conversion is in the neighborhood of $20,000. Far more than the value of the car.
While a great deal of those costs can be reduced if you’re willing to DIY it with a junkyard motor/transmission. Assuming you aren’t particularly fussy about everything working properly, we are again in the area of lumping.
For about the same money a Modern Jaguar V8 could be used, gain even more power and be considered an upgrade rather than a Lumping.
It’s not just the engine/ transmission though. The Jaguar HVAC system, electrical system, coolant system all deserve an upgrade from their 40+ year old origins.
Investing that much money or money and labor. Without retaining originality is almost a sure death sentence to the car. While the person doing the work involved knows what parts were used the dealership will not. Nor can you expect independents to risk their time and reputation trying to repair a modified car without proper service manuals and parts availability.

Most of the nearly 20 new cars I’ve bought were Chevy’s. I like them. But all of them needed service work. Indeed scheduling maintenance was never a simple drive in affair. Rather a compromise between my schedule and theirs. ( we me typically at the losing end). That’s not bad service, that’s the reality of operating a expensive service department.

I understand buying a 30-40 year old car is a hobby. They will need far more work than any modern car. You do it out of love, not for any practical reason. If your choice is to re-engineer your car, that’s your choice. Just don’t be offended when others question your choices.

 

I have to respectfully disagree with the premise of your post. The price of a conversion in some measure depends on where you live. Like any reasonbly technical piece of mechanical surgery, it is best left to someone who has a successful track record, and there aren't many who can make that claim. Because of the availability of kits for doing these conversions, cost savings and consistency of the product can be achieved. The same cannot be said for dropping any other engine in our cars. A remanufactured LS1 motor and kit are still far cheaper than an XJR motor. Most of the benefits of either motor are lost unless matched to a 4 speed transmission. Again the GM 4L60 or 4L80 are cheaper than and superior to what is attached to jaguar motors.
I do agree that it is easier to get an appointment for service at a jag dealer than a GM dealer, but at considerable cost. Labor rates and parts at the Jag dealer are known to be leading cause of mortgage refinancing. It far less necessary to use GM dealers at all since so many mechanics are quite familiar with the LS1 family of engines. You are also correct that some mechanics will shrink away in fear when they see a car with a transplanted motor, even if the engine is a species they have worked on many times. The more elegant the installation, the less justified that is. There are, however, scores of hack jobs and DIY efforts that will cause even a conversion specialist to turn tail and run.
Finally, it has been pointed out many times that a LS1/4L60e is capable of achieving 20 mpg at the upper limit of highway speeds while factory Jag drivetrain is happy to see 15. A 25% fuel bonus is achievable over the full driving range which is a nice dividend over 50,000 miles.

 

This is aways a continuous debate. I have owned various Jags over 49 yrs, been working on my own for 53. Sure, talk of dealer prices, gas mileage and how hard it is to work on them. But, if you knew this, why did you buy one? Is it money, prestige or dream? I own 2 Mark 1s and am in restoration on my own. I own two newer model MINI Coopers and an LR4 ( with Jag 5.0 L engine ) only been to dealer for electronic diagnostics, I now own diagnostics. These to me are not expensive to fix as parts to drive line is common to other 4X4s. Engine was Ford, says fomoco on block and oil cap. My V-12 XJS was a hoot to drive and the only problem was if you did not drive it enough, you would get a leak, same as XJ6, 120-150. I'm told that I am lucky because I can do the maintenance and repairs. My answer is "I can read" I buy the manuals, tools and have the space, so I can enjoy these cars. Tullius did not win his Championships with Chevy engines. I can overhaul a maintained xk engine for $800, takes two months working in garage at night. There is nothing better than taking the V-12 XJS and beating stock Vipers and Vettes. So I don't understand this debate. I really don't get the Ford hotrods with a chevy engine. If you can't afford it, learn it, read the book and do it. These cars are not about cheap, they are about looks and history. Longest production V-12 and 6s. Drive'm like you don't own it. 100 mph runs every week keeps them in shape.

 

WARNING: Lots of inaccurate information in this post.

Not so. I just paid 625$ for a complete XJR drop out with all accessories. Some 4.8/5.3 LS engines are bargains and sometimes can be found for under 1000$. The lower cost stuff usually has been hastily removed with a fork lift with many broken items. The more desirable LS1 / LS2 / LM4 / LQ9 (Alu cathedral port 5.3 and 6.0) are selling for about 2000+ depending on mileage and specifics. L79/ L92 square port stuff is $3000+ Rebuilt crate LS motors are 3500+ $ as a starting point with no intake or accessories.
Bottom line, it can be extremely expensive to do an LS project in any car unless you have a complete and suitable donor of which there are few. Some LS projects can cost 20k+ and that starts to get silly when there are boat loads of great performance cars full of modern features for 15k or less.


The 4l80e was "attached" and used by Jaguar on the 1995 to 1997 XJR and 1994 to 1996 v12 XJS and XJ sedans.
The 4L80e is kind of a slow and lazy transmission with poor gear ratios for a car. It's widely accepted that the 4L80e is durable but no fun to drive when compared to other contemporary transmissions like the 4L60e or ZF 4HP24


Dealerships are independent and make their own rules on what they service to some degree. Around here. My local Chevy dealer will fix any car, they need the work. My local Jaguar Dealer, Ray Catena, is like a palace and turns away older cars, they just say... "Its not worth fixing, wait here I'll get the new car sales manager to speak to you now."

No convert will be well serviced at a dealer other than basic stuff like oil and brakes, most will turn away project cars. Converts are best serviced by and enthusiast, those that did the converting, a local specialty shop or DIY'er.

Not my experience, I put a Jaguar 1995 AJ16 in a 1976 Coupe and would routinely manage 23 MPG or more in some certain situations. I daily drove the car for quite some time before selling it on BAT and always found the fuel mileage exceptional.

As I always say, it your car and your money do as you please but lets try to be accurate for the benefit of others who may not know the facts. Getting in front of the KB and spewing inaccuracies seems to be a social phenomenon in all aspects of society and we are all going to pay a price for this durge of misinformation. Perhaps we are 'post truth' and there seems to be no limits to it.

 

please do a little more research. In the 4th quarter of 1977 Jaguar switched from the Borg Warner transmission to GM’ transmission for V12’s and the late ones used the 4 speed. So if you want a GM 4 speed on your earlier ones, go ahead and hook it up. Fair notice: Jaguar Chevy and other GM products each got their own different bell housing. The internals are the same but the casing varies.
With regard to fuel mileage it honestly depends on how you drive any car so fuel varies. Many people report 18-19 mpg with the later 6.0 engines.
Since the XJR engine is supercharged you are speaking apples and sardines. Yes a super charged engine will be more expensive than a normally aspirated engine. Please look up the price of the Supercharged LS engine before you claim it’s cheaper.
As far as reliability and quality please spend a few days at your chevy dealership. Their cars need work too and some owners wind up very unhappy just like Jaguar owners and every brand. But you won’t find any 30-40 year old Chevies going in for service. To most people they are merely transportation. Not as loved as Jaguars are.
Finally engine swaps in general. People buy cars for emotional reasons. A Jaguar is an expensive car and like all expensive cars depreciates quickly. Someone comes along and buys a used Jaguar thinking what a deal they got on such a special car. Grace, space, and Pace like the Jaguar slogan says. But hey keeping it in good condition is expensive.
So they think putting a cheap engine in it will make it cheap to run. It’s not!!!

 

Having spent decades in dealership parts and service departments, I agree. Yes, policies vary but most are a bit selective about what they'll take in. Only in rare cases did we take on specialty cars, project cars, converted cars, and so forth. For some really good customers we'd make an exception. Or we'd sometimes make an exception if we were absolutely sure the work required wouldn't end up being a can of worms.

In most dealership shop there is a very strong emphasis on production. There are xxx-number of mechanics, xxx-number of bays, and xxx-number of hours in a day. The idea is to cultivate the right mix of work to maximize usage of those resources to produce billable labor hours. Project cars, hobby cars, modified cars, most older cars are a sure way to bollix up the mix

Cheers
DD

 

I apologize for not doing my research on the transmissions used in later Jaguars. Never had a later one. The remanufactured 4L60e with the GM bellhousing can be had for under $800. Of course, the price and availability of remanufactured drivetrains will vary depending where you are.
I do not agree about the apples and oranges. If you are going to replace an engine in a Jaguar and want fairly good performance at a reasonable price, remanufactured, not used, jaguar engines, supercharged or otherwise will cost you more than a stock LS1. Folks on this forum may be so savvy that they can source Jag motors with equivalent performance motors for less and find someone to drop them in, but in my experience shops that work on Jags charge a lot more than the guys who do LS1 conversions. Sure, you can pay big dollars for an LS1 if you want to big HP numbers, but a stock remanufactured 5.7 LS1 can be had for under $1000 and I have 2 to prove it: The Caprice Interceptor in my XJ6 and the Buick Roadmaster in my XJS-C. And I was not unhappy to see that v-12 go away.
I am not sure what a "drop out" is, but I suspect it is a used motor. I don't buy used motors unless I intend to rebuild them [as I did with the 96 5.7 vortec out of a Chevy Suburban that I "marinized" for my Bayliner]. And yes, $600 is a probably a good price for a used motor but that is apples and oranges to this discussion of remanufactured engines.
BTW, my comments about mpg were meant as comparisons between the v12 and the LS1, not an XJR motor. Of course mileage will vary depending on how heavy your foot is. My comment was based on information from a friend with a 95 XJR who says he never got better than 17-18 at 70-75 mph highway.
Engines don't fail that often. What they do is nickel and dime you with all the emissions and accessories that do have limited lifespans. The EGR valve for the LT1 ranges from $40-60; the XJR $50-160. An LT1 O2 sensor ranges from $19-32; XJR $63-90. AC Delco 140 amp LT1 alternator is $109 [no core required; XJR 120 amp is $152 including a $45 core charge. LT1 water pump is $54-102; XJR is $64-290. And so it goes.

 

OK I’m confused. Are you a DIY guy or a have it done guy?

The following is a gross generalization and there are certainly plenty of exceptions. However in general Premium cars such as Jaguars, Ferrari, Aston Martin etc. command very expensive labor rates.
Two reasons for that. First they are not bread and butter cars with plenty of common knowledge . Instead they are relatively rare that demand a high amount of not just parts replacement but trouble shooting as well. Not even specialist shops fully understand everything. Thus they are expensive to work on.
Second, if you can afford to buy it you can also afford to pay to maintain it. More than one “valve Job” or “overhaul” has been sold to make a payment or because the mechanic wanted to see what was inside the engine.

• I started collecting V12 engines. Many Engines came from a shop that specialized in swapping them out with Chevy engines. Others came from wrecks, and badly rusted cars. I quit when I had 50 on hand. Out of 50 junk engines only 2 were outside factory specs. One the oil filter hadn’t been tighten and all the oil pumped out on the way home. Even when a set of con rods had knocked a hole on each side of the engine he kept driving. ( Not the engines fault) the other one was caused by trash between the A/C and radiator. It dropped valve seats. ( Not the fault of the engine) the rest were all within factory specs. 48/50 junk engines!!!!
  Yes mechanics without proper training we’re guessing as to why they didn’t work. A common fault known to Chevy mechanics is an ignition unit fail. About $35. The same one Jaguar dealers charge $5-600 for! Exact same one!
  or the Miles of vacuum hoses could have a leak. ( one goes all the way into the trunk where the ECM is ). Countless issues with those hoses. Or synchronizing the butterflies.
  Up into the 1990’s there was no OBD2 to plug in and have it tell you what to fix. So mechanics had to figure it out themselves.
  OBD2 solved all those problems. And later ones with it have a great reputation for reliability.
  VW came out with fuel injection for their Rabbit. And early Jaguars simply used 3 of them for their fuel injection. 3x4=12
• Through the 70’s-80’s- early 90’s all fuel injected cars had the same problems. You don’t see a whole lot around. Especially luxury cars.

 

I agree with you. Engines don't fail and can operate even when you think they shouldn't. I had a 1990 Buick Reatta with the generic GM 3.8 V6. After 180k I thought I'd treat the motor to a dose of Slick 50. Only after did I learn that the 90 cam bearing casting was slightly off. The motor spit a cam bearing into the pan but continued to run despite almost non-existent oil pressure. I
'm a little of both, but more DIY simply because I can't afford to do otherwise. Still, I don't want to invest the time and effort into a project gambling on a used motor even though the odds are good that I'd get lots of miles out of it. I had someone do both conversions because I don't have the skills to get make sure the conversion will satisfy CA smog refs, get GM to talk to Jaguar, how best to route exhausts, what manifolds work best in the jag engine bay, and so on. A few of the conversion kits are pretty complete and the instructions are pretty good. I did do a project on a smog exempt 73 XJ6 using a small block 400 out of a truck. Lots of things didn't work, but the car filed the bill being fast and beautiful. I just threw in the whole drivetrain which included the Turbo 400 trans. Was really dissatisfied with that combo.
What did you intend to do with all those V12s?

 

i have known MG for a few years, he is an OK guy!
but he is an old timer , and a good debate gives him the energy to keep going, something to look forward too!
i know this because i'm an old timer also! older than MG, got my 1st car when he was born!
chances are today niether of us will ever build another competitve TOP LEVEL race car again!
if you read thru some of his posts over long term you can understand him!
ron

 

I’m a racer. I’ve raced Jaguars my whole adult life and never once had an engine fail on me. I built my XKE V12 roadster when they were still fairly new and thought I’d need a spare or two. I paid $500 for my first one and what I offered went down from there. In the end my average price I paid for a V12 was $128. ( a fair number were free )
Anyway the first engine I built was simply a development engine nearly stock except for Weber’s and headers. But my second was a full tilt double boogie serious race motor. Bored to 3&3/4. Forged pistons w/ 13.1 compression. Offset ground .200 aftermarket racing rods, ported oversized titanium intake valves. ( 1.90 ) Billet camshafts oversized lifters, due to increase in lift and duration. Triple disk 7&1/4 flywheel and clutches. Senz 5 speed with dog rings. Quick gear selection change ( take apart the transmission change gear ratios to suit track and conditions and reassemble in 10 minutes.

Anyway my thought is that others would want the V12 and since I was getting them so cheap I quit when I got to 50.
I started selling them. I found out how hard it is. I started asking $1000 and if they haggled I’d go down to $700
I only sold one or two a year barely enough to pay for the advertising. Mostly to people who just wanted to have one or take one apart. In the end I had 35 left so I pulled those apart to separate the aluminum from the steel to get the best scrap metal price. The two I got that were bad were just given to me so I really only paid for around 25. A lot of them came from a guy who swapped in Chevy junkyard motors.

 

Guilty as charged. I am an old geezer who loves to share my knowledge. ( thank you for your kind words). I think I’ve learned more from you than you have from me. You’re brave enough to drive a modified Jaguar on the street. I don’t think I could ever do that.
I can’t afford or justify racing at the top level so I do Vintage and want to do $500 car racing ( LeMons and Chumpcar). My first attempt fell afoul of the spirit of Chumpcar but the rules have stabilized enough to attract me back.