High guys. I would love to get your perspective on how the XJ6 platform drives. Here is my dilemma.

I am am searching for a 2nd toy to flank my Huracan. Wanted to keep it under $30k but could spend more if must. I have owned Iike 100 cars including a new 2011 XKR and a user 2003 XJR. Been a while since I've owned a Jag. This time I was originally shopping American muscle for contrast. I ended up driving a MK 2 restomod with a small block and auto and was smitten! It felt tight, lively steering with performance steering wheel, looked great, no rattles and was quite quick!

Then I realized the XJ6 also have V8 conversion - in fact moreso as I see plenty in the market. But before I fly to see one I'd like to better understand how these feel. Do they drive "lighter" than the 2003 XKR? With a swap do they feel lively and sporty in the steering and chassis? I am guessing the MK 2 feels sportier due to being lighter and also paradoxically taller so when it handles well it subconsciously defies your expectations.

 

Is the lack of response indicative of very few in the forum having V8 conversions? Even so you stock XJ6 owners could provide feedback on handling/feel in comparison to the X308 no?

I will try to find one to drive as well!

 

I have a high HP SBC conversion. Probably the most refined and powerful small block XJ around. Look up my posts and check out my videos.

The driving feeling is excellent and improved just as you described because of weight reduction.

The GREAT thing about series 1/2/3 sedans and coupes is that all the performance oriented parts from the XJS are a bolt on. XJS V12 front and rear sway bar in a light weight V8 conversion are very nimble package. With Alu head, intake and modern A/C compressor you can really drop a lot of weight off the nose of and XJ and it's a chassis and suspension design that can handle a V12.

Here is a list of Performance mods.

Engine
Professional built buy a local machinist with decades of racing experience.
Engine was built as a tribute to John Lingenfelter and done just like he would have based on his books on the subject. It really paid off.
Small block Chevrolet, 406CI,
10.25:1 compression
AFR CNC 195 heads
Comp cam
Johnson Lifters, roller rockers
Lingenfelter Super Ram intake
32Lb injectors
Northstar derived crank angle based ignition with full ECM control
GM 1227730 ECM hacked with many additional features such as EVC and Launch Control.

Transmission
700R4
Transgo Shiftkit
1800 Stall converter with lockup.
Performance steels, wide band and upgrade 7 piece clutch packs.
Billet Survo
Transmission was built personally by a local guy who has been building for 30 years.

Cooling
Performance radiator
Dedicated transmission, oil & power steering coolers

Suspension
Match set of springs from a I6 1995 XJS
XJS front and rear sway bars
XJS Bilstein Shocks
Late XJS ZF aluminum rack.

Exhaust
Custom pressure wave termination box with dual outlets, one outlet is muffled, the other is un-muffled with a ECM controlled dump valve. Dead quiet when cruising, obnoxious at WOT.

Brakes
Front custom spindles with Wilwood 12.2 inch alu hat rotors and 4 piston calipers
Rears, XJ8 derived outboard 12 inch vented rotors and OE calipers.
3 channel ABS

Differential
3.54:1 gears with an Auburn locker center section.

Comfort
Nice sound system, heated seats, XJS climate control, power mirrors, key-less entry, one touch windows control, Auto dimming rear view mirror

Chassis
Reinforced and Lightened extensively with dimple dies. Everything was changed for weight savings. For example... Alu and nylon bolts and nuts were used in select areas and things like window motors and mechanisms were redesigned for weight savings.

Setup
Engine was pushed back as far as possible for balance. Custom mounts based on the XJR fluid filled mounts for noise harshness and vibration control were fabricated.

Tuning
Car engine and transmission has been impeccably tuned for performance, responsiveness and readability. It has a dead smooth idle despite the performance cam. I just finished this... took months of work few days a week. Many parts such as lifters, injectors and a ignition had to be redesigned to meet performance and NVH goals.

Body
Euro lights, euro bumpers and rear wheel arches were tastefully widened 1.25 inched for bigger 17 inch based wheels and tires.

The car is a serine animal. Very comfortable, very powerfully, very controllable and very fun. I've modded many performance cars over the years, this is the most capable and comfortable one by far. Most of this was a DIY endeavor so I dont think I'm anywhere near 30K.

Come to NYC, see a show, have dinner and drive my Coupe. You'll want one on the spot.
I've got two more coups in the works, one a 350 HP 6.0 V12 with traction control and ABS. The other is a 600 HP Single trurbo LT1 with traction control and ABS too, this car is gonna need steam roller out back and will probably get broadspeed fenders.

 

Wow, that is some build! Great insight thank you very much. Is the platform torsionally rigid and does it rattle?

 

From the factory mid 80's sedans are the most rigid and offer a solidity about 10 years ahead of their time. The 70's and early 80's sedans are a bit less rigid becasue of lower quality steel, fewer welds and less panel dimpling. To me the mid 80's cars feel more rigid and more direct than the Late 80's XJ40 series. A rare moment in automotive history where the previous model was widely considered superior to the newer model in some respects.

The 70's coups are wet noodles, not rigid at all. Those that have been driven suffer badly form stress fractures in specific areas. If you jack up one corner of coupe the doors will mis-align... to the point they will be difficult to open and close. When I was done with my coupe... the doors open and close exactly the same jack'ed up or not but some flex is still measurable with instruments.

I reinforce them and they need it. Watch my vid's.... You can see it in the wheel wells. I insert a 3.5 inch thin wall tube in the length of the sills. It's welded in strategic places on the end and along the length with bracing to create a stiff ladder. I used all the techniques seen on Fiboy's coupe but to the next and much higher level.

Out on the road...the end result is a rigidity about the same as mid 90's BMW 7 series. No too bad for a classic car considering all the wheel and suspension upgrades.

As for Rattles, the front and rear subframes do a really good job as isolating the resonance that leads to rattles. The design is way ahead of its time and remarkable rattle free even with out the chassis stiffing. We've got lots of rough roads here in NYC so I'm talking from real world experience.

The most solid and rigid cars I ever owned were an Audi A8, that car felt like it was CNC'd from a solid block of Aluminum. The 2nd was a BMW 850ci. 3rd is a Lexus RX400h. No way to get a 70's or 80's jag to that point with out a major redesign of some of the aesthetic parts for stiffness and the look of the car would have to change.

 

How much extra bracing do you need to put into the car to cope with the extra torque flex? Does the firewall need to be upgraded too? Is the V12 stiffer, & therefore better suited to cope with the upgrade?

 

I've observed no chassis differences on a v12 car.

Not much extra metal, probably 50 lbs worth. but it need to be in specific locations. So how do you know the locations? That's easier than one might think, Jaguar gave us the answers... The XJS floor pan is an evolution of the XJ floor pan and one can clearly observe where Jaguar added extra metal, bracing and triangulation on the XJS. Many of those features can be transferred to an XJ chassis. There are some major differences between the XJS and XJ. The firewall on an XJ can be triangulated just like an XJS. I've done this on a car, and not done it on another with a similar setup it makes a major difference in cowl shake and overall feel.

We know the XJS platform was WAY ahead of it's time. Aston Martin used it until 2004. That's saying something.

 

no comparison, the MK-2 is a rear-stiff axle whereas the XJ-6 is IRS (independent rear suspension). The Ride of the MK-2 is quite harsh, the ride of the XJ-6 is smooth.

the handling of the MK-2 is to say the least, dangerous at 80+ mph in heavy turns.

The car has a tendency to lose contact with the pavement in one of the rear tires, because the axle travel is short and in a very twisty turn, the axle will keep the tire high and from making contact with the pavement. Old symptom of the MK-2. However this does not happen at 60mph, it's only at high speeds where the lean and weight of the body defeats the rear suspension capabilities.

this doesn't happen with the XJ-6. No comparison. The S type, factory-coded "MK-3" during its development, does not suffer from this weird deffect because it was built with the IRS too.

 

Yes and no. I'm not seeking to argue the IRS vs "solid" suspension. Way above my pay grade.


Last night, as I dozed in my comfy recliner, I watched a segment of "Counting Cars".
The "Count" visited the Shelby Mustang and more works. The head guy took Danny for a ride in a Shelby "Daytona" coupe. Infinite power. The "solid" axle did not appear to limit hard turns with "power, lots of it" on....


Carl

 

The only way to test Oranges to Oranges is to put an IRS in that car & compare it's lap times. The live axle might be competitive on a smooth track, but as soon as things get bumpy my money would be on the IRS.