Hello all.

firstly, if your response is why the hell are you doing this, save your time, and be negative on another thread.

I’m in the process of making my Xjs a grand tourer that’s more capable of being grand on rougher roads.

I want to drive it to Dakar.

a quick google of safari rally Porsche/ or even historic rally will show my intended end result.

my Xjs is Now a 4.0 manual. It was previously an auto 3.6. Soon to put in an xjr6 engine.

it will have sump guards and full under tray skid pan.


ground clearance. My current, and I think easiest solution, is to use the v12 front springs. The weight not being there with the v12 will give, hopefully around 2” of lift?

as for the rear, I don’t think the gaz height adjustable shocks will give enough lift to balance the stance and clearance?

any help from anyone that has done a rally conversion, your input would be greatly appreciated.

Happy new year to all.

 

How much have you got to spend?

 

I would be sourcing and repurposing used parts where possible as naturally a sump guard or under tray are not off the shelf Jag parts. I can weld, and fabricate.

I’d say budget wise for just the suspension, £1500?
Can be stretched if necessary.

all labour would be done by myself.

 

Krakenfelt,

I don't know if you can get the clearance that you want but have a look at this current thread and the photos of the Gaz shocks on my 4 litre convertible. It might give you an idea of how much more clearance you can get over standard ride height.

1994 XJS rear shocks - Jaguar Forums - Jaguar Enthusiasts Forum

Cheers

Paul

 

Thanks Paul, some good information there. I notice on your Gaz’s you have a lot of thread that could be used in either direction, especially to gain height. I’m guessing the convertible is heavier in the rear so that spring rate on a coupe would add even more height.

 

In no particular order, to have a chance of finishing a rally:

• Roll cage to stiffen the passenger cell
• remove rear subframe and weld strengtheners all over it, including top shock attachment points
• solidly bolt rear subframe into the car
• the front subframe will ideally need solid mountings too, though this will greatly increase harshness in the cabin. A bit of beefing up would not go amiss here either
• pass the brake and fuel lines inside the car, they are under the floor
• skid plate protect: the diff, the radius arm attachment points to the shell, and the prop shaft
• run the sump guard right back to include the gearbox
• there are line fuses all over the XJS, fuses in the engine bay, etc etc. Ensure the fuses to all the important circuits are relocated inside the car. VERY carefuly check all wiring and renew where not supple, upgrade any iffy connectors
• ride height: you are limited to, effectively, jacking up the car with longer springs, or as you mention stiffer ones. At the rear convertible late model springs are far stiffer than your OEM ones and will jack up the car quite noticeably. Together with platform adjustables (AVO or GAZ) that will do your two inches easily. At the front you can pack them and get about 2 extra inches at the wheelarch easily with v12 springs. At the rear probably about the same with adjustable platforms. However with standard rear adjustable platform shocks you will limit rebound travel quite a bit which may break the shocks under harsh conditions. Having done this your geometry will be all over the place as a result so it, particularly camber, will need fixing. Some rear negative camber is essential for decent XJS cornering, the rears are limited to what you can adjust, and the more the car is jacked up it gets more limited. The fronts also will run out of adjustment quite quickly when jacked up to this degree.
• the front of the monocoque across the gap in front of the radiator will need extra bracing.
• the front shock wing-strengtheners, welded into the inner wings will need extra strengthening to the chassis rail
• the rack will need protecting underneath, right to the steering arm ball joints
• fit dual circuit switchable fuel pumps and clear the tank/boot/battery area for quick servicing and changes
• An ally radiator (ebay has loads, not expensive) will take a noticeable amount of weight out of the chassis ahead of the front axle and improve turn-in a great deal. Dump the aircon stuff and add a mesh stone guard.

None of this is expensive, mainly your labour. Have fun!

 

Somebody did this to a Bentley Continental GT:

https://www.roadandtrack.com/car-cul...uild-for-sale/

Might give you some ideas.

 

Clarkson did that om the latest Grand Tour episode for their safari trip

 

Sound like amazing fun, wish I could do this. I know nothing about rally'ing but I do know much about driving on the mean streets of NYC. The pocked and cratered surface has taught me much about wheels and tires. Sometimes there no place to go but up a curb. So with that in mind I have a few thoughts.

Taller tires... The XJS uses a 26 inch tire in an OE configuration. You can easily run a 27 inch tire or perhaps a bit more. That'll net you a 1/2 inch or more. I run a 27 inch tire and my car is lowered. I'd try to get as much as you can in the tire, becasue using a taller tire for clearance wont mess with your suspension geometry. You can alter the panels in the wheel well for some more clearance. Consider making new panels or the judicious use of a dead blow hammer.

I'd focus on motion control with uprated shock and not necessarily stiffer springs so the suspension can move, flow and roll with it.

Front suspension
Space out the lower spring pan for the front using a 3/4 inch spacer at the bottom on the spring. That should net you the other 1.5 inches of lift for the front. I'm not sure I'd run v12 springs, might be too stiff and make your front suspension reactions jouncy.
I'd run the poly forward front subframe mounts. The OE rubber wont last but solid/rigid mounting will cause things to break. The p/n for the front pair of bushings is SPF1005K. The bushings on the rear of the front subframe are very robust but I'd upgrade to grade 8 bolts and bring a few spares.

Gonna have to get creative the front shocks. The OE pencil tubes just dont have enough oil volume and will quickly become foamed and over heated. At the very least I'd try to fit a larger shock with more oil volume. Choose a larger diameter shocks like a Bilstein from later 2001 XJ8 or XJR
SF
Rear suspension.
For the rear I'd stick with the stock 4 shock arrangement but perhaps upgrade to Bilsteins or KYB. There should be enough oil in the 4 shocks to survive heavy usage.
For the height, weld up a new mount to the top of the lower control arm, saddle style. Also add a smallish 1/4 inch spacer to each of the 4 spings. This will keep your stock shock travel as long as possible.
The 4 stock rubber mounts need to be helped out. You will need to brace the IRS. If you search for IRS brace here you will see many ways to do this. I wouldn't rigid mount the IRS or the braces... just firm things up to help the OE bushes survive. I think SNG Barret sells the harder and more durable cage mount that was used on the DB7 GT. I would replace the smaller trailing arm bushing with poly. The part number here is SPF0789K

You certainly will need to drop the cage and weld a 3/16 inch piece of plate to re-inforce the area where the shocks mount. I've seen this area fail. The cage will want to pull apart so you will also need to re-inforce the area the runs across from the cage mounts to the diff where the it has been opened up so the exhaust pipe can pass. This thin area curls and snaps.

Brake Lines.
Consider steel braded lines a the wheels and you can box in the exposed lines that runs to the back with hat channel

Fuel Lines.
Cover up with hat channel

That's about the best you can do with a $1500 budget.

 

thanks all for the very concise advice! i will be commencing work on my project as soon as lockdown is lifted here and i can go to the workshop.

has anyone done a coilover conversion on the front?

if i were to get 'non xjs' rear shocks, what parameters would i be working within? shock length and diameter of mounting eyelet? does anyone know these measurements?

also, my xjs has the sportpack anti roll bars, would it be better off without them for rallying?

my conclusion from weighing up what i need to get out of the car, has arrived at being able to adjust the shocks to gain ground clearance yet also be able to lower to get a reasonable highway cruising set up. i had toyed with the idea of going for air suspension, as it would give me 'on the fly' adjustment, and also an air compressor. this would be useful if i am lowering tyre pressure regularly depending on conditions. however, the air suspension world seems to exist purely to accommodate 'stance' being very very low ride height. i want the opposite. also, i presume at maximum height the shocks would be very very firm...

 

is this the db7 part that you mention? seems very pricey for something that could be made relatively easily.. https://www.ebay.co.uk/i/13335528033...saArehEALw_wcB

 

That is a bracer for the rear axle cage, in effect it bolts the bottom of the cage to the car body, thus removing acceleration and braking loads from the rubber mountings. And yes, you can easily make one. My own view is that adding bracing across the front of the car (OEM there is one diagonal brace) is very important for body flex protection.

 

I can offer nothing but encouragement. Please post pics!! Would like to see the donor vehicle pre-op. Really, really interested in the driving dynamics and just HOW offroad you can go with it. Bravo!