The Jaguar Mk X  and 420G 1961-1970

Years MK X 3.8 1961 (October) - 1964 (September)
MK X 4.2 1964 (October) - 1966 (December)
420G 1966 (October) - 1970 (August)
(page last  modified 12/98)
See also Jaguar 420 (Mid sized model derived from the S type, with the same 4.2 engine)
Notes 1961 was a year of renewal for Jaguar. In that one year it replaced the venerable XK range of sports cars with the exciting new E Type (or XKE) sports car, and a few months later  in October showed the all new replacement of the MK IX, a design which had not changed much since the launch of the MK VII in 1950.

Both these new models had some pieces of their design in common - both featured the triple 2 inch carburetored version of Jaguars new 3.8 XK engine, as had been fitted to the XK150 "S" , both had monococqe bodies, replacing the previous models body on chassis construction, and both featured Jaguars new design independent rear suspension mounted in a separate sub-frame, which it turned out was still being used 25 years later in the XJ6.

There the similarities between E Type and MK X ended. The MK X was a massive car meauring 16 feet 10 inches which was almost 6 inches longer than its predecessor the MK IX (and about  22 inches longer than the contemporary MK II). It was also extremely wide, at 6 feet 4 inces.  The only dimemsion which was reduced when compared to the MK IX was the height, which was reduced from 5 feet 3 inches  to 4 feet 6 3/4 inches. Some of this reduction was due to the adoption of 14 inch wheels, rather than 15 inch.

Being longer and lower the MK X 's bulk was quite well disguised, and apart from the somewhat bulging sides, the car looked quite sleek.  The car retained some of the styling cues of the "big" Jaguars. The chome plated window frames, and the imposing radiator, which was now sloped forward to reduce the height at the front. For the first time on a Jaguar a 4 headlight treatment was used.and the traditional Jaguar horn grilles were retained. Power assisted steering was standard, and the car was availabel with 3 speed Borg Warner automatic transmission, or a 4 speedmanual box. 

Inside the MK X was traditional Jaguar luxury with leather seating, and walnut wood. The dash was the new "corporate" design of the 1960's that had originated with the MK II in 1959, but with much more extensive use of wood. veneer. split bench front seats were used, and the rear seats had individual picnic tables that folded down from the back of the front seats.

The MK X 4.2 was introduced in October 1964 for the 1965 model year, and in general received the same mechanical updates as the contemporary E Type. The engine was further enlarged to 4.2 liters, and the transmission was either the new all synchromatic 4 speed, or a newer design Borg Warner Model 8 automatic. An alternator replaced the generator of the previous model, and power steering and braking systems were improved. Air conditioning became available as an option in 1966.

For the 1967 model year the designarion was changed from MK X to 420G.  This was in line with the model policy at the time, when all Jaguars models were being rationalized.  The MK II range became the 240 and the 340, and the new 420 was introduced as an intermediate model between the MK II and the MK X. The changes to the MK X were cosmetic only, but quite distinctive. Most noticeable were the radiator grille which was given a distinctive central vertical bar, side repeater flashers, and a new hub cap design. In addition the car became available with two tone paint finishes, or, when   painted in a single color, a chrome strip down the waist line was employed, where the divider line would have been for two colors. Inside the car, crash proofing was improved by fitting a black padding to the top of the dashboard, and the clock was moved from its position in the rev-counter, to a separate fitment in the top crashproofing of the dash. Perforated leather was used for the seats.

The 420G became the last survivor of Jaguars extensive 1960's range of cars, all of which were killed off after the launch of the XJ6 in 1968.  Production of the 420G actually continued well into 1970.

Description 4 door sedan (saloon), monococque construction
Colors See the large sedans colors page
More Pictures
Exterior and Interior
Jaguar MK X sedan
Jag1.jpg (19243 bytes)

courtesy Joel Kimball Ventura, CA

Model Engine Bore/Stroke Power
MK X 3.8
MK X 4.2
3781cc 6 cyl twin ohc
4235cc 6 cyl twin ohc
4235cc 6 cyl twin ohc
87 x 106 mm
92 x 106 mm
92 x 106 mm
255/265 bhp @ 5200 rpm
265 bhp @ 5400 rpm
265 bhp @ 5400 rpm
Note on BHP figure for 3.8 Our thanks to Tage Bengtsson of Sweden for pointing out the discrepancies in quoted BHP for the 3.8 model. Various sources quote figures of 245/255, and 265 bhp. Indeed two different 1962 brochures quote 255 and 265 figures. It may be that the figure varied somewhat by market, and by the compression ratio of the engine. The normal figure was 8:1 but 7:1, and 9:1 ratios were available from the factory.

In 1968 with the introduction of the S2 E-Type, the USA version of the same 4.2 engine that was fitted to that car was equipped with two Stromberg carburetors, rather than three SU units. Its not known if the 1968 and up 420G's destined to the States suffered a similar modification.

Carburetors Triple SU 2 inch HD8 (all models)
Engines are 3.8 and 4.2 versions of the XK engine
Brakes Four wheel discs, rear discs are inboard. Vacuum servo assist (Dunlop)
(Various sources differ, slightly)
MK X 3.8 (RHD) 9129 Total 12977
MK X 3.8 (LHD) 3848
MK X 4.2 (RHD) 3720 Total 5680
MK X 4.2 (LHD) 1960
420G (RHD) 5429 Total 6554
420G (LHD) 1125

Grand total   (RHD) 18278  (LHD) 6933  (All) 25211

MK X 3920-4032  pounds
Length 16 feet 10  inches
Height 4 feet 6 3/4 inches 
Width 6 feet 4 inches 
Fuel Consumption 3.8 13.6 mpg
4.2 15.8 mpg
Performance Top Speed 119 mph (3.8) , 122 (4.2)
0-60 mph 10.8 secs (3.8 Auto) , 9.1 seconds(3.8 manual), 10.3 secs (4.2Auto)  
Wheelbase 120 inches
Wheels/Tires 3.8                            Dunlop 7.50 x 14 on 5 1/2K x 14  steel wheels
4.2 and 420G           Dunlop 205 x 14 radials on 5 1/2K x 14  steel wheels
Transmission 4-speed manual.  optional  Borg and Warner DG 3 speed automatic transmission. (3.8), Borg Warner Model 8  (4.2 and 420G).   Laycock de Normanville overdrive optional on the standard transmission car.
Front Independent. wishbones and torsion bar, anti roll bar
Rear Independent.
Engine Numbers 3.8             ZA1001 or ZB1001 and up
4.2/420G  7D50001 and up
Chassis Numbers BW Suffix indicates fitment of Borg Warner automatic transmission
DN Prefix indicates fitment of overdrive (De Normanville)
MK X 3.8 300001 and up - Right hand drive
350001 and up - Left hand drive
MK X 4.2 ID 50001 and up - (RHD)
ID 75001 and up - (LHD)
420G GID 53001 and up - (RHD)
GID 77001 and up - (LHD)
Recently an apparently genuine  420G with number GID 76799BW came to light. Was this car built as a MK X and "comverted" by the factory?
Standard Equipment Leather seats (perforated pattern on 420G), disc brakes, power assisted steering.
Options Air conditioning (from 1966), electric windows, heated rear window, Radiomobile radio and speakers, rectangular fog and matching spot light. Automatic transmission, or overdrive for manual transmission