Production years: 1966 - 1971

In 1966 the Mark 10 was re-badged as the 420G with a modicum of trim changes like new chromed hub caps, a bold centre rib in the radiator grille and some interior trim changes. The model, although running alongside the all new XJ6 when introduced in 1968, was finally dropped from the range in 1971.

Model Summary

Model Type:

Mark 10/420G/DS420

Production Dates:

1966 - 1971

Engine Range:

3.8 Litre Saloon

4.2 Litre Saloon

0 - 60 mph:

3.8 Litre Saloon - 9.1 seconds

4.2 Litre Saloon - 9.9 seconds

Top Speed:

3.8 Litre Saloon - 119.5 mph

4.2 Litre Saloon - 121.5 mph

420G Technical Specifications

Technical Information

Engine Statistics

  3.8 Litre Saloon
Engine (cc) 3781
Bore and Stroke (mm) 87 x 106
Compression Ratio 8:1 (7:1/9:1 optional)
BHP 265
@ RPM 5500
Torque (lb ft) 260
@ RPM 4000
Fuelling 3x SU carbs
  4.2 Litre Saloon
Engine (cc) 4235
Bore and Stroke (mm) 92.07 x 106
Compression Ratio 8:1 (7:1/9:1 optional)
BHP 265
@ RPM 5400
Torque (lb ft) 283
@ RPM 4000
Fuelling 3x SU carbs

Engine Performance

  3.8 Litre Saloon
Top Speed 119.5 mph
0 - 60 mph 9.1 seconds
Fuel Consumption 14.1 mpg
  4.2 Litre Saloon
Top Speed 121.5 mph
0 - 60 mph 9.9 seconds
Fuel Consumption 14.5 mpg

Model Specifications

  3.8 Litre Saloon
Transmission 4-speed (3 synchro) BW 3-speed auto
Wheel Size (in) 14, steel
Suspension (Front) Ind semi-trailing wishbones, coil springs, anti-roll bar
Suspension (Rear) Ind lower wishbone/upper driveshaft link, radius arms, coil springs
Brakes 4-wheel disc, rear inboard
  4.2 Litre Saloon
Transmission 4-speed (3 synchro) BW 3-speed auto
Wheel Size (in) 14, steel
Suspension (Front) Ind semi-trailing wishbones, coil springs, anti-roll bar
Suspension (Rear) Ind lower wishbone/upper driveshaft link, radius arms, coil springs
Brakes 4-wheel disc, rear inboard

Model Dimensions

  3.8 Litre Saloon
Length (in) 202
Width (in) 76
Height (in) 54.75
Wheelbase (in) 120
Front Track (in) 58
Rear Track (in) 58
Weight (Cwt) 37
  4.2 Litre Saloon
Length (in) 202
Width (in) 76
Height (in) 54.75
Wheelbase (in) 120
Front Track (in) 58
Rear Track (in) 58
Weight (Cwt) 37

Optional Extras

  • Choice of three radio installations with or without rear parcel shelf-mounted speaker
  • Electric radio aerial
  • Wind-up radio aerial
  • Electrically operated windows (front and rear)
  • Laminated windscreen
  • Witter tow bar
  • Heated rear screen (earlier cars)
  • Front seat belts
  • Choice of radial, town and country, or whitewall tyres
  • Borg Warner automatic transmission
  • Overdrive (for non-overdrive-equipped manual transmission cars)
  • Fire extinguisher
  • Sundym tinted windscreen and side windows
  • Wing mirrors
  • Integrated ignition/starter switch to steering column
  • Limousine appointments (only available on ordering a new car)

Model Contacts

Nigel Thorley

Nigel Thorley

Magazine Editor & Seminars

Need a manual or Buyers Guide for this model?

Visit Shop