I’m a newcomer to Jags. My 77 XJ12 (with 350 Chev) is 520mm at the middle of the headlight, not 619mm as the book says. Previous owner recently fitted 30mm lowered springs from a reputable supplier Kings who only make a 30mm drop. Not sure why I have a 100mm drop in height.
I have the old springs and will put them back but am hoping they were not sagged. Previous owner said he replaced them because his son used to get carsick!!
It looks good under the front end, bushes in good condition.
Why would it sit so low?
A picture would help, a 100mm (4”) drop is extreme and I would have thought to be almost on the bump stops?
The car is up on stands at the moment, doing sway bar bushes.From top of rim to guard its 122mm front and 132mm rear ( rough measuring though). Rear is 196mm from bottom of crossmember, book says 189mm plus/minus 6mm.!
(upload://a4DU3UwjdHZJiFThoDFrkvIWrAd.jpg)
I assume you don’t mean that the spring itself is designed to be 30mm shorter under load? That would indeed give you about 75 mm drop in ride height.
I like the “rake” look of a lowered front. It usually comes with sagging OEM springs. But then, the rates have gone down and the ride is too soft. If you have clearance between tyre and top of wheel well, and a good spring rate, I like it and would leave it along (except if you have to have the bow tie, at least consider painting it red 
).
BTW, usually the problem is the opposite when replacing the heavier twelve with an SBC, but you can add spacers at both top and bottom of the springs. Each factory 1/8" spacer raises ride height about 5/16" IIRC, regardless of what spring rate you have and regardless of the weight being supported.
Looks like the car originally had a vinyl top?
The lowered spring is supposed to lower car by 30mm.
Will consider changing the colour of the bowtie lol. The previous owner removed all the Jaguar insignia on the boot too. Although there is a Jaguar emblem on the lower fender with 350 below it.
Why do you believe it may have had a vinyl top? Original colour was maroon.
There is a chrome trim piece (or appears to be) at the bottom of the c-pillar that was associated with vinyl tops, at least on S1 cars. It covered the edge of the vinyl, and wasn’t included on S1 cars with painted tops.
**
I assume that Kings did their homework, Leon, using the original springs’ characteristics to compute the desired lowering - being aware of the weight differences between the V12 and the Chevy. This likely also involves stiffening the springs to ensure against excessive bump stop bumping, as Robin mentions in another context…
Complications also includes owner actions. The ride height adjustments involves packing rings - which likely were originally fitted. If not replaced the ride height will be lower. However, reputedly a max of 4 packing rings are to be used on each spring - which gives a max variation of some 30 mm, so does not fully explain your 100 mm…
Another factor is also how ride height measurements were taken - depress front bumper, lift and slowly release. Of course after the car has been rolled to stabilize suspension. Again, unlikely to fully explain the extreme lowering result measured.
The reason for the PO’s change of springs is somewhat dubious - it is the shocks, combined with spring rate that prevents ‘wallowing’. And some kids get carsick no matter what…:). But unless you have actually accessed the springs to see what is what - you don’t really know what’s what…
Another issue hee is that suspension geometry specs are given for a specific ride height - indeed, for precision, setting tools are prescribed for proper settings. And while the suspension set-up is specifically designed to avoid geometry changes with suspension movement - some changes are unavoidable, but usually not too detrimental to car behaviour…
Overall, I suspect that the new springs are the direct cause of the low rid height - and refitting the old springs is likely the easiest way to restore it. Normally, sagging springs are countered by adding packing rings - up to a point…
Frank
xj6 85 Sov Europe (UK/NZ)
**
Yes there is chrome trim piece both sides so probably came with a vinyl roof. Thanks for the info.
Kings recommend leaving out the packing rings when fitting their springs. They also make a spring specifically for Chev engined XJs but I’ll have to check see if these have been fitted.
Cheers
Noel
XJ12(350) AUS.
Noel:
Gee, that car looks great t that stance. I like it. But, clearly, it is your car and should be what you like !
Yes, As Frank opines, wallowing is usually related to poor shock absorbers. Uncontrolled jounce and bounce !
My car with the DOHC was pleasing low in front. I liked it . but, spring sag at 115 miles, a bit of a surprise. When the SBC went in, it lost about 100 pounds. the front came up a tad. I measured it. Now, right at spec. Still OK with me.
Bob. Naah, whoever heard of a red bow tie !!!
When I built my Hot Rod of the forties, I lowered the front, a lot! I had the front I beam bent by a local specialty shop a full 4". And I added another 12" or so, by reversing the spring eyes.
It looked so much better ,
Low is sleeeek .
Carl
**
As we do not know how many packing rings were fitted with the original springs, or indeed the original ride height, Noel - the recommendations seems a bit rash…
If indeed 4 packing rings were fitted, which is not beyond the probable; 30 mm on the shortened spring would be added to 30 mm from the missing rings…
Frank
xj6 85 Sov Europe (UK/NZ)
**
With the old springs in it’s sitting slightly higher than std. These lowered coils (which are specifically for Jags XJ6’s with a Chev engine) are 50mm shorter than std unsprung, may explain the 100mm drop installed?
**
The background shows a difference of nearly 7,5 cm rather than 5 cm, Noel…
Remove 4 packing rings from the original spring set-up - and you have the 10 cm. One problem here is simply that the PO changed springs for other reasons than ride height - and you have no data on the ride height with the original set-up.
Another is that the respective spring rates cannot be read by the pictures; if the intent was to lower the ride height by 3 cm with the lighter V8 - something has gone wrong. And only partially due to the possibility of ‘illicit’ removal of 4 packing rings from the original set-up. It would only alter the ride height by 3 cm…
Casting no aspersions; at this stage I can see no better progress than installing the old springs - and measure the ride height. If it can be brought up to specs using packing rings; the replacement of the springs were uncalled for in relation to ride height. And you would likely be well served with the original springs…
Frank
xj6 85 Sov Europe (UK/NZ)
**
Don’t let the picture fool you Frank, the difference is most definitely 50mm. Those lines correspond to the highest point on each spring. Put it down to parallax error.
The original springs are now in with 2 spacers. Height is a fraction higher than Std V12 height (619mm). The spring manufacturers claim a reduction in ride height of 30mm with these springs over a std XJ12 and are specifically made for XJ6/12 with a 350 Chev fitted. They also recommend the removal of the original spacers when fitting their springs. I found 2 spacers with each lowered coil.
At this stage I’m going to stick with the original springs and see how it settles over time .At least I can slide a jack under it now.
**
I expected something like that, Noel…
Whatever the ‘fault’ with the lowered springs - the purpose of the springs is to hold the body up. As the original spring rate was used for the heavier V12, and likely perfectly OK for the lighter xk engines; you will experience the ‘Jaguar ride’ with the Chevy…
In other words, the PO’s decision was unwarranted - and based on extraneous factors…
Frank
xj6 85 Sov Europe (UK/NZ)
**