I'm starting to see the attraction in lumping a older XJ-S. The flathead pre-HE just doesn't lend itself to daily driver duty. What other engines would be a good fit? I'm thinking +300HP, +25mpg, including rwd +4speed automatic. That's from the factory, no modifications needed.

Ford's new "ecoboost" 3.7 V6 looks like a good candidate.
305HP, 280FTLBS, 31MPG, 6 speed automatic.
Fords new "5.0" also just makes the economy criteria.
412HP, 390TQ, 26MPG, 6 speed auto.
Porsche GTS 3.8Liter for grins....
408HP, 310FTLBS, 25MPG.
Nissan 370Z - a few years in production.
3.7liter, 332HP, 270FTLBS, 7 speed automatic.
Audi S4
3.0liter, 333HP, 325FTLBS, 28MPG... except AWD trans!
Any others, preferably available used?

 

Be prepared to open up your wallet if you're trailblazing. I would stick with a proven package, such as provided by Johns Cars in Dallas.

Jaguar conversions, swaps, parts, service and advice - from John's Cars in Dallas.

 

You'll never recoup the fuel savings and the blow to resale with what you save on fuel. Save a Jag, sell it and buy another car.

 

What about a Jaguar XJR supercharged I6 320hp 378tq and 21mpg this would as easy as an LS1 conversion as the AJ6 was used in the XJS. The money saved over engineering something custom would give you many years of fuel.

Anything other than what is available from places like Johns Cars, Jaguar Specialties or Jaguar would require custom engineering. Mounting an engine is not just a matter of building mounts and plonking it in - it needs to be lined up so pinion angle is correct and the engine is central, otherwise you will end up with vibration. Then there is integrating the newer engines ECU and BCM into the XJS if it not an engine that has been used in conversions before you will require custom modification of the ECU to ignore the BCM as most have some kind of security that prevents the engine from starting without the correct inputs from all of the other onboard computers.

 

If you really want an XJS lump, someone from Seattle just posted here in the XJS section with a lumped convertible, asking how much it was worth because they need to sell it.

 

Here's the thread JameyXJ6 is talking about:

https://www.jaguarforums.com/forum/x...ertible-66308/

Already lumped, been sitting for 4 years. Might just need a battery & fuel system flush.

 

I appreciate the concern but that math doesn't add up. In my case this is as opposed to buying a new car. The payments, full coverage insurance, gap coverage, and so on cover an awful lot of gasoline. Since the XJ-S is going to be restored anyway, it's a sunk cost and doesn't apply. The different engine costs would.

Looking into other Jaguar engines was my next bit of research. Jaguar XJR supercharged I6 320hp 378tq and 21mpg sounds pretty good. Rare as hens teeth?

The multiplicity of computers and sensor inputs from undesirable areas (ABS, or anything else the '78 doesn't have) would definitely rule out some engines.

Never have liked convertibles, but thanks for the tip.

 

I wasn't referring to a new car. You can't compare a 30-year-old car to a new car in any plane. Leave the Jag as-is and get a $500 Hyundai for a daily driver.

 

I DO think it would be neat to put a newer Jag motor in.

 

I own 2011 F-150 FX4 with "Ford's new "ecoboost" 3.7 V6 looks like a good candidate", BTW, it is 3.5L, not 3.7 and it is amazing. One thing though, you ain't gonna find one cheap, however if you did, 6 speed ZF transmission on it is almost the same as on 2003+ XK8/XKR, plus one extra clutch disk per all 6 speeds.

 

About 6500 were built. I think half that came to the USA.




Or at least really complicate things.

The supercharged XJR/6 engine is a difficult swap into an XJS for physical fit reason, as well.

You might wanna just buy an XJR outright. Before buying an XJR I had both and XJS and an XJ6. I found the XJR replaced both very well, combining luxury and performance.

I still miss the other two, though.

Cheers
DD

 

Whoops, meant "3.7L Ti-VCT V-6 Engine", the mustang engine. Thought I saw ecoboost.

 

Just go simple, get nice 3.0l Supra turbo JDM motor + trans and you will love the result. I believe it was done with XJS and TH400 before.

 

That does probably make the most sense economically. But life is too short for boring cars, and I drive a lot. 30,000 miles a year or so.

 

Jaguar : XK Jaguar : XK | eBay

Something like this XK8 would be less than the cost of lumping an XJS.

IMO, the pre-HE XJS will likely be more collectible than the more common HE versions. And once you lump it, they become very hard to sell. There are a LOT of them to be found already at giveaway prices.

 

I would recommend going with a proven combination like Johns Cars. They have the most complete kit AFIK. You can also look at Suncoast conversions as well. A bit cheaper, but less complete. The Jaguar XJR6 would be fairly difficult as sorting out the electronics in the engine and transmission is not for the faint-hearted. Jaguar World had an article about two or so years ago about someone trying it. He got the engine in after some wrangling, but I don't think he ever got the electronics done. I think he ran out of money and time and had to back-burner the project.

As mentioned earlier, getting an early model XK8/R would be cheaper, but it seems you are intent on keeping the XJS.

 

Now drooling over 3.5L, twin turbo, 365HP, 420TQ, est 29MPG HWY in car, ecoboost V6.

 

YEESSS!! i hate to admit it BUT, that FORD twin turbo, Direct injection ECOBOOST is a work of art in engineering, and the best part is it works, lot of torque, great mpg, light weight, whats not to like??

OH darn, its the money part, in time they will be available in junkyards, but thats a few days down the road!

by then there will be more choices of engines.

turbo, DI inj. and smaller engines are on the way.

for myself, i'm waitng for one of those 2011 JAG XFD 2.2L DIESELS, 50mpg , 0-60 8sec, 140mph on the top end.

YUP sounds like a plan.
lotta nice stuff coming down the road.

Ron

 

A new 5.0 Ford Coyote crate motor is over $7,000 without the ECU and wiring harness- add another $1200. A 3.5 Ecoboost crate motor (if they sold one) would likely be in the $ame range. That takes those off the table for me, at least for a car like this.

There's nothing wrong with a lump as daily driver (mine actually has a small block Chevy). It's just real hard to make an economical justification for the swap. By the time you procure all the parts, pieces, and misc components, you will have spent more money than it would have cost to buy another car.

I'm actually considering a retro "anti-lump" using a 4.2 liter XK engine, triple SU's, and a five speed. I can probably get at least 250-260 hp out of it, similar to the XKE ratings. It wouldn't be as fast, but it would be interesting. It would be all Jag,and it would sound pretty cool too.

 

John of johnscars says "my kits end with the 97 LT1 - vortec old style yes - new alloy LS = NO, they do not fit well"