New: XJSC LS/6-speed Manual Trans Project
 

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Hello all, this is Andrew from Jaguar Specialties. As many of you know I’ve been a long time XJS owner (since at least 1992) and have owned my current 1988 XJSC for over 15 years. Although I haven’t posted here in a while, I regularly read the forum, which has always been interesting and informative.

From a purely technical interest standpoint, I wanted to let the forum know of a new XJS project we’ve embarked on. This same XJSC was converted with a 1997 Camaro SS LT1 engine and 6 speed manual transmission back in 2002/2003 which had been great fun, and we did a full detailed writeup on the process on our website back then (still posted). But now our focus has been on the newer GM LS engines and we’d never done a LS/manual trans into an XJS. So to that end, we’ve begun the installation of a 2002 Camaro LS1 engine and T56 (6 speed) into this car. And while this base LS1 engine makes a modest (by current standards) 325 hp, these engines have great power potential, in our case helped greatly by a planned free flow intake, a 2 ½” mandrel bent full dual exhaust system, and some tuning. Also, from a weight standpoint, this all aluminum package saves some 350-400 lbs over the V12 drivetrain and even offers a near 100lb savings over the previous alum head/iron block LT1. (that last bit should be obvious visually once the new engine is in and we see how the car sits)

The project will also be something of an update for the car- freshening that (still, after 30 years) original front suspension and trading up to a late model XJS rear unit with 3.54 gears and outboard brakes. There will be no love lost getting rid of the original 2.88 diff that (in combination with the 6 speed manual trans) gave nearly 60 mph in first gear and something on the order of 1400 rpm at 85 mph in 6th gear. Interestingly, even though that setup was way overdriven in terms of gearing, the engine never felt lugged, thanks to the great torque available down low. The 3.54 should be quite a difference, quite snappy to say the least.

Again, this post is made purely to share interesting technical details on this approach with the group and nothing more. Our first installment has been posted and you can find it here: Jaguar Specialties


Thanks,

Andrew
Jaguar Specialties

Weights...
 

We've had the cars (XJS, coupe) on a scale before and after conversion and they go from right at 3900 down to just under 3600 and that's with a small block chevy with cast iron heads and block. The LS is easily 100 lbs+ lighter than that. And then I believe the 6 speed manual is also a weight savings over the T400- maybe 30 lbs total

Note- I've seen that 680 lb number for the V12 before- from experience, I find it unrealistic....

That's where my numbers come from...

Andrew

I would expect more than 30lbs difference from a TH400 to a manual. While I've not weighted the 6 speed used behind an LS motor. The TH400 is a huge transmission. I expect that the torque converter would weigh 30lbs or more just by itself.

Weights.....
 

But remember a manual trans flywheel is much heavier than a flexplate. I'd guess that the TC vs flywheel/clutch combo may be a wash, weightwise.

Regardless, the major weight savings is on the other side of the flywheel- the engines.... 30-50 lbs vs the 300-400 difference V12 vs LS is almost in the noise...

nice i look forward to seeing more on this. also sounds like i may be over estimating the weight on my car. iv been estimating its weight at 3800 lbs mine is a convertible but everything for the power top has been removed factory seats were replaced with aftermarket and a few other small weight savings iron gen2 lt1 engine currently still has iron vortec heads. will be getting changed out to aluminum high performance heads in the future and has about 80lbs worth of forced induction bolted to it. maybe im not that far off but the idea it might weight somewhere in the 36-3700lb range makes me happy...lol i should really get around to putting it on a scale

id love to see some details on a ls swap xjs. i think the oil pan could be problematic although i know they have come out with a number of oil pans for muscle car swaps that may alleviate that problem.

im running 3.54 rear gears with a 700r4 and will shred tires at pretty much any time at will in 2nd gear. tops out 2nd gear around 75 and cruses in overdrive around 2400 rpm i think you guys will really like the 3.54's in your setup.

Keep in mind that the Convertible was the heaviest XJS produced. It was approximately 400 lbs heavier than the Coupe because of the amount of chassis reinforcement required = 4256 lbs curb weight from the factory with the V-12. The XJSC maintained a rigid roof framework and I think came in about the same weight as the coupe.

now you done dashed my hopes and made me look up factory published curb weights for 1993 (same year as my car....lol)

3759 lbs 4.0L coupe
3970 lbs v12 coupe
4034 lbs 4.0L convertable
4233 lbs v12 convertable

looks like right at +260 lbs for a convertible.

figuring the majority of other weight savings are eaten up by my blower setup so i think we can pretty safely call that a wash using there 300lbs weight difference between a v-12 to iron head iron block sbc i should be more like 3900 lbs. so i might have been underestimating vrs over estimating. so looks like about 100 lbs weight savings going from a 4.0L to a iron v8 with a 200lb difference between the v-12 and 4.0L sounds like the factory published curb weights seem pretty close as the v12 coupe matches what they have weighed them at

but then there should be roughly a 40lb difference when i swap to aluminum heads, spare tire jack and tools are probably worth another 25-30 lbs. then if they used a cast iron intake manifold on there swapped cars that is substantially heavier than an aluminum intake. im just going to have to weight the thing next time i get a chance....lol

Just a note...........
 

Just a note here- Only the manual trans aspect here is new. We have offered an XJS-LS conversion kit and supporting parts as regular items for almost 10 years now. The whole LS conversion process is well understood- oil pan, exhaust, proper modern cooling system, gauges, all of it. But that kit supported an automatic trans (4L60E or 4L65E), and I imagined it would be good to have the manual trans version in our product portfolio, so that's where we are now... The point is an LS-powered XJS is not a mystery but a reality.

You can peruse several completed cars (most done by customers) on our website- here:

Jaguar Specialties

Again, just offered in the spirit of interesting technical content......

nice i wasn't aware anyone was making a ls swap kit for them already. let alone for the last 10 years. there is defiantly value in something that has already been sorted, you probably know better than anyone here sorting out the details is often times the most time consuming part of a engine swap.

does your manual transmission kit address the pedal assembly considering very few xjs's ever came factory with a manual transmission?

Pedals for manual trans....
 

The pedal deal is actually not a problem- we have several suppliers who can rework an automatic pedal box into a manual unit. Actually, the auto pedal boxes have 90% of what we need to be manual units already- they were just never finish machined. BTW, same goes for 70-87 XJ6.....

What we've done in the past (for other manual trans conversions) is connect the customer and the pedal box supplier directly and they do that transaction on their own. Saves a few $$...

i kinda feel as tho i am left out,, i had my XJS weighed at a reputable weigh station and weight slip says 3395 lbs,?

if i can find slip i'll pic it? been 10yrs or more , i dont think it got heavier over time?
or i'll go back and get it reweighed?
ron
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I was going to buy an XJ-SC with an LT1 lump. The T-tops and GM1 V8 gave me a strong urge to paint a screaming chicken on the hood.

.

GOOD idea , be the only one around, RARE!!!
ron

Is that a real convertible, or a cut down coupe???
 

Is that a true convertible- something built as a convertible from the factory?? Judging from the doors (with the wing windows in them) it looks more like a a coupe that maybe had the roof cut off. I'm not seeing any top mechanism there either- does it have a roof....??? That may explain the weight question....

And it doesn't look like a Hess and Eisenhardt either....

Even so, I'm not sure the 3395 is likely.....

the car was sold new in 1978,as a coupe in Kent England, later around 1980/83, it was done as a prototype cabriolet by Aston Martin coach works, who were almost bankrupt at that time period!
Jag had little capital also ,they helped out A/M, with staying afloat!
car was shipped to USA 1986, by a woman ,related to US ambassador , Virginia/DC!
car was put in a NJ warehouse for some yrs, never run,loss interest or something!
finally advertised in WALLSTREET JOURNAL, old guy in Fla, bought it sight unseen.
he died and car was sold off as estate sale, i ended up with it,, it was rough!

so after 3 yrs, and over $40K , it cost much more to raise the dead than to breed a new one!!
ME ? i,m an old fashioned American hot rodder , gotta do everything my self, just so i have a reason for exsistance !
WELL after looking at the profile of the AM rendition of a cabrio, i cut the the rest of the B post and relate stuff, and end up with a nice looking car!(my opinion).

fact is when at a show , people walk by all the rows of Jag converts and coupes ,
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stop by mine and many questions, and marvel at a real V12 cylinder engine!

some pix of the 2 hr video during resto/mod etc.
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RON

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some times projects never are finished , so for a top, your in Cali. remember the CARSON REMOVABLE HARD TOPS.

i,m working on some ideas like that, aluminum frame and covered with material/insulated , but the profile is going round in my head, so far not what i have pictured!??
car does have modded drive train and suspension,, Wilwood calipers,EBC slotted rotors, SS lines , 700R4 trans built, modded final drive ,3.73 gears HD LSD.

ron

its for SALE also.

It seems my technical thread got hijacked.... :)

!

SORRY Guy ,I got carried a way, never meant too!

ron