Jaguar XJ6 / XJ12 and Daimler Sovereign /Double six - Series 1

Production Years XK6 2.8
XJ6  4.2
XJ6L 4.2
Sovereign 2.8
Sovereign 4.2
Sovereign Double Six
Sovereign Double Six VP
September 1968 to August 1973
September 1968 to August 1973
October 1972 to August 1973
July 1972 to August 1973
October 1972 to August 1973
October 1969 to August 1973
October 1969 to August 1973
August 1972 to August 1973
September 1972 to August 1973
See Also Jaguar 420 (immediate predecessor model)
Jaguar XJ6/12 and Daimler Sovereign Series 2 - superceding model
Timeline for the Jaguar models
(coming soon)
Notes If the reader has read the pages devoted to the other Jaguar models of the 1960's, it will be readily apparent that by the middle of the decade, Jaguar had changed from having almost too slim a model range in the 50's, to great overlap in the 60's. The reasons for this are explained elsewhere in this database, but it has much to do with the perceived failure of the big Mk X model in its intended primary marketplace - the United States. The Mk X was certainly not a bad car, it had impressive engineering for its time, but some of the reasons put forward to explain its relatve failure were that it was simply too large for its home market, the United Kingdom and that in all markets  its styling was somewhat controversial (always a matter of taste). The early 60's was certainly the time when muscle cars were evolving in the States, and they had sharper more angular  lines, and better straight line performance. Against this the Mk X's styling was curvaceous, and its straight line performance lacking, although it certainly handled better..   

In reaction to this, Jaguar evolved a range of cars for almost every possible segment of any market. Central in this policy was the development of the S-Type Jaguar. Most sources suggest that originally the S-Type was to have been the next in the range of compact Jaguar sedans, and indeed its internal code name was Utah Mk III, (where the MK II was Utah Mk II). However as the Mk II range was still selling reasonably well in 1963, the decision was taken to sell the S-Type as a new model alongside the Mk II range. This inevitably led to overlaps in the range, as the Mk II was available with a 2.4,3.4 and 3.8 liter engines, and the S-Type with 3.4 and 3.8 engines. Markets such as the United States overcame this by simply not selling certain models, such as the 3.4 S-Type, and (after around 1964), the 3.8 MK II.  

What does all this have to do with the XJ6 you may ask?  Well there is one more step in the story, and that is the 420 model, introduced in 1966. In hindsight it was very much a stop-gap for the XJ6.  Jaguar had several reasons to wish to streamline their large range of cars, but the most important two must have been a) the sheer expense involved in producing so many model variants, and b) the impending introduction in the United States of safely and emissions legislation. Certifying so many models was going to be prohibitively expensive. The 420 is significant in this account, as the ultimate development of the compact Jaguar range, which had evolved from the Mk I of 1956, through the Mk II of 1959, and the S-Type of 1963. The 420 was essentially a 4.2 liter S-Type, but with the styling at the front changed to a family resemblance of the 4 headlight treatment of the Mk X model. It was also designed to be a model which could shore up sales in markets where the 3.8 S-Type, and Mk X models (renamed 420G at this point) were either two underpowered, or too large. The 420 is also very significant as the first Jaguar model sold almost unchanged, except for badging, as a Daimler. Of course the earlier Daimler V8 models had been based on the Mk II, but had at least retained their Daimler engines. The Daimler Sovereign was sold alongside the 420, and was essentially a 420 with all the options.

The XJ6 with the existing 4.2 liter engine could be certified to meet the impending American legislation, and so, from its introduction (in September 1968) on, the various other models were dropped, the last being the Mk X (then 420G) itself in 1970.

Mechanically the XJ6 series one was quite similar to the 420 model. In size it fell somewhere in between the 420 and the MkX/420G. Comparitive leading dimensions are provided on a separate page.  Much was done to improve Jaguars already impressive chassis engineering, and items such as a double bulkhead between engine and passenger compartments to cut down on transmitted noise, and tuning of the front and rear subframes to reduce road noise made it a superbly refined car. In addition the brakes were improved, with new three piston calipers in the front, and larger tires (up from 185 to 205 size) improved handling.

Styling was somewhat interesting. As with almost all Jaguar models, Sir William Lyons oversaw its design closely, and it showed definite family resemblances to both the 420 and the 420G, but with a refinement of lines which were all its own. Upon its introduction it was immediately called "The most beautiful car in the world" by some of the motoring press. The 420 and the 420G were already somewhat similar in their styling at that point, albeit different sizes, and to give a very quick summary, the XJ6 took those lines in a size which was in between the two, and straightened some of the curves, while retaining the same overall styling.

Because the new XJ6 had to replace so many other models, it was available from the outset with two engines, the first was the familar 4.2 liter XK engine taken more or less straight from the 420. This was the twin SU version, which had been rated at 245bhp in that model. In the XJ6 it was rated at 180bhp, but perhaps this is simply because manufacturers were becoming more forthcoming about quoting true net figures by that time, not gross.  The second engine, also an XK unit was a development of the 2.4 engine with a capacity of 2792 cc, and quoted at 150bhp

The XJ12

From its introduction the XJ6's engine bay had been designed to accept the V12 engine under development, and first fitted to the series III E-Type (XK-E) sports car in 1971. This engine was made available for the XJ range in July 1972, and the resulting model was called the XJ12. Apart from the engine, the major mechanical changes were ventilated discs at the front, and slightly stiffer front springs, as the V12 was some 80 pounds heavier than the XK unit,

The long wheelbase models

One of the only criticisms levelled at the XJ6 when compared to its competition was its slighly ungenerous read seat legroom, and this Jaguar remedied in time for the UK Motor show of 1972 by stretching the car by 4 1/2 inches. At first the standard and lonh wheelbase cars were sold in parallel, but in later Series II days, the original wheelbase cars were dropped.

The Daimler variants

Just as they had done with the earlier Jaguar 420 model, Jaguar rebadged the XJ6 as a Daimler. The external differences were mainly the use of the traditional fluted Daimler grille, and a fluted rear revesing lamp housing. The hood was also fitted with a central chrome strip. The Daimler "D" replaced the Jaguar head on the wheel hubs. The Daimler models were fitted with all the options, the few manual cars for example, had standard overdrive, Both six cylinder engines were available, and the model was called the Daimler Sovereign. The Daimler equivalent to the XJ12 was the Daimler Double Six, and it was actually the Daimler that was first stretched 4 inches to become the Daimler Double Six Vanden Plas.  These modifications were included in Jaguar models a month later

Description 4 door sedan (saloon)
Model Engine Bore/Stroke Power
Sovereign 2.8
2792cc 6 cyl twin overhead camshaft 83 x 86 mm 150 bhp @ 5500 rpm
Sovereign 4,2
4235cc 6 cyl twin overhead camshaft 92.7 x 106 mm 180 bhp @ 5500 rpm
Double Six
5343cc V12 90 x 70 mm 250 bhp @ 6000 rpm
6 cyl models) Twin 2 inch SU HD8 (HS8 from 3/71)
V12 models 4 Zenith 175CD SE
6 cylinders engines are versions of the Jaguar XK type DOHC inline 6
for details of the V12 engine, see section - The Jaguar V12 engine (will be added shortly)
Brakes 4 wheel Girling discs. Front discs featured a three piston caliper, up from previous models two. 

(Various sources differ, slightly)

Production numbers for both Jaguar and Daimler series 1 cars.
abbreviations used
lhd - Left Hand Drive, rhd - Right Hand Drive, swb - Short wheelbase, lwb - Long wheelbase

XJ6 2.8 19,322 (approx 1 lhd to 2 rhd)
Daimler Sovereign 2.8 3,233 (assumed mostly rhd) Total - all 2.8 models   22,555
XJ6 4.2 (swb) 59,077 (approx 2 lhd to 3 rhd) Total Jaguar 4.2 models 59,951
XJ6L 4.2 (lwb) 874  (1 known lhd, all others rhd)
Daimler Sovereign 4.2 swb 11,522 (assumed mostly rhd) Total Daimler 4.2 models 11,908
Total - all 4.2 models  71,859
Daimler Sovereign 4.2 lwb 386 (assumed mostly rhd)
XJ12 swb 2,474 (1 rhd to 2.5 lhd)
XJ12L lwb 754  (3 known lhd, rest rhd) Total Jaguar V12 5.3 models 3,228
Daimler Double Six (swb) 534 (assumed mostly rhd) Total Daimler V12 5.3 models 885
Total 5.3 models  4,113
Daimler Vanden Plas (lwb) 351 (assumed mostly rhd)

Totals  - All XJ6 models - 79,273. All XJ12 models -3,228. Total all Jaguar models - 82,501
Total Daimler models - 16,026
Grand total of Jaguar and Daimler models - 98,527

2.8 models 3640 pounds
4.2 models 3696 pounds
V12 models 3920 pounds
Length XJ6/12 and Daimler swb models  15 feet 9 1/2 inches
XJ6L/12L and Daimler lwb models 16 feet 2 3/4 inches 
Height all models -  4 feet 6 inches 
Width all models -  5 feet 9 1/4 inches 
Top speed 4.2 manual 124 mph
4.2 auto 120 mph
2.8 manual 117 mph
2.8 auto 113 mph
5.3 auto 130 mph
Wheelbase Standard (short)  108.75 inches
Long wheel base 112.75 inches
Transmission all synchromesh, 4-speed manual with optional Overdrive
Also available, Borg Warner 3 speed automatic. Early 4.2 cars have Model 8, replaced later with Model 12. XJ6 2.8 models have Model 35 gearbox. 
All V12 models were only available with the Borg Warner automatic transmission. Model 12 was usedl
Front Semi trailing, double wishbones coil springs and anti-roll bar
Rear Independent, lower wishbones, radius arms and twin coil spring/damper units per side..
Steering First use in a Jaguar sedan of rack and pinion steering. The system was by Adwest.
Chassis Numbers
BW Prefix indicates automatic (Borg Warner) transmission
XJ6 2.8
XJ6 4.2
XJ6L 4.2
Sovereign 2.8
Sovereign 4.2
1G1001- and up (RHD models), IG50001 and up (LHD models)
1L1001- and up (RHD models), IL50001 and up (LHD models)
2E1001- and up (RHD models), 2E50001 and up (LHD models)
1T1001- and up (RHD models), IG50001 and up (LHD models)
1U1001- and up (RHD models), IG50001 and up (LHD models)
1P1001- and up (RHD models), IP50001 and up (LHD models)
2C1001- and up (RHD models), 2C50001 and up (LHD models)
Engine Number prefixes XJ6 2.8
XJ6 4.2 and XJ6L
XJ12 and XJ12L
7L      See also the engine numbers page
Standard Equipment Almost all cars, except for 2.8 'base' model have leather seating. 2.8 'base' model has the Ambla interior.
Air conditioning standard on all V12 models
Powrlok differential standard on V12 models
Overdrive standard on all manual transmission Daimler models
Options Power steering - almost universally fitted as standard, except in 2.8 model
Laycock de NormanVille overdrive on manual cars
Borg Warner auotmatic gearbox
Power windows
Air conditioning