Model Designation:
Jaguar 420G (Post-1966)
Production Years Covered:
1960, 1961, 1962, 1963, 1964, 1965, 1966, 1967, 1968, 1969, 1970
Positioning:
Luxury saloon car, positioned as a premium offering from Jaguar.
Competitors:
Rolls-Royce Silver Cloud, Bentley S-Type, Mercedes-Benz S-Class of the era.
Design Philosophy:
Combines Jaguar's characteristic blend of performance, luxury, and elegant styling.
Distinguishing Elements:
Spacious interior, independent rear suspension, powerful inline-six engines, advanced features for its time.
Engine:
Complete engine overhaul, tuning, diagnostics
Fuel System:
Carburetor systems (SU HD8, Zenith-Stromberg), fuel pump, fuel lines
Cooling System:
Radiator, water pump, thermostat, hoses, fan
Ignition System:
Distributor, coil, spark plugs, wiring
Exhaust System:
Manifolds, pipes, mufflers
Transmission:
Manual and Automatic (e.g., Moss gearbox, Borg-Warner DG150/DG250)
Drivetrain:
Clutch, driveshafts, rear axle, differential
Suspension:
Front independent suspension (double wishbone), rear live axle with trailing arms and Panhard rod
Steering:
Power steering system (Burman-Marles/Adwest)
Brakes:
Disc brakes (Dunlop/Girling front and rear), brake system hydraulics, parking brake
Electrical System:
Wiring diagrams, lighting, instrumentation, starting and charging system
Bodywork:
Body panel repairs, door mechanisms, glass, trim
Heating And Ventilation:
Heater matrix, airflow controls
Maintenance:
Routine servicing, lubrication, fluid changes
Troubleshooting:
Diagnostic procedures for common and uncommon faults
Repair:
Step-by-step repair instructions for all major components
Rebuilds:
Complete engine, transmission, and differential rebuilds
Adjustments:
Carburetor, ignition timing, valve clearance, brake adjustments
Electrical Diagnostics:
Fault finding for electrical systems with detailed wiring diagrams
Depth:
Comprehensive (from basic maintenance to complete disassembly and reassembly)
Presence Of Illustrations:
Yes
Illustration Types:
Hundreds of photos, drawings, and detailed diagrams
Illustration Detail:
Enlarged insets for detailed part examination
Instruction Format:
Numbered, step-by-step instructions
Special Notes:
Notes, cautions, and warnings integrated into procedures
Table Of Contents:
Numbered and easy to use
Engine Type:
Inline 6-cylinder, DOHC (Double Overhead Camshaft)
Displacement:
3.8 Liters (3781 cc) for early models; 4.2 Liters (4235 cc) for later models.
Bore X Stroke 3.8L:
87 mm x 101.6 mm
Bore X Stroke 4.2L:
92.07 mm x 106.68 mm
Horsepower 3.8L:
Approx. 220-230 bhp at 5500 rpm
Torque 3.8L:
Approx. 242 lb-ft at 3000 rpm
Horsepower 4.2L:
Approx. 246-265 bhp at 5400 rpm
Torque 4.2L:
Approx. 283-318 lb-ft at 4000 rpm
Carburetors:
Twin SU HD8 (3.8L) or Triple SU HD8 / Zenith-Stromberg CD200 (4.2L)
Fuel Type:
Premium Unleaded Gasoline
Compression Ratio:
8.5:1 (standard)
Compression Ratio:
8.0:1 or 8.75:1 (depending on market/tune)
Transmission Type:
4-speed manual with Laycock de Normanville overdrive (optional on some early models)
Transmission Type:
Borg-Warner Model 8 (early models) or DG150/DG250 (later models) 3-speed automatic
Overdrive Engagement:
Electro-magnetic switch on gear lever stalk
Automatic Transmission Fluid:
Likely Dexron II or equivalent (refer to specific manual section for precise identification)
Automatic Transmission Capacity:
Approx. 8-10 pints (depending on model)
Length:
Approx. 196.5 inches (4991 mm)
Width:
Approx. 70 inches (1778 mm)
Height:
Approx. 54 inches (1372 mm)
Wheelbase:
Approx. 117 inches (2972 mm)
Curb Weight:
Approx. 3700-4000 lbs (1678-1814 kg)
Standard Tire Size:
6.40 x 15 or 7.00 x 15 (bias-ply); radial equivalents common for modern use.
Bolt Pattern:
5 x 4.5 inches (114.3 mm)
Oil Change:
Every 3,000 miles or 6 months (typical for the era)
Grease Points:
Regular greasing of suspension and steering components is crucial, often at every oil change.
Engine Oil:
SAE 20W-50 or SAE 20W-40 (depending on climate, synthetic oils can be used cautiously)
Coolant:
50/50 mix of antifreeze and distilled water
Brake Fluid:
DOT 3 or DOT 4 (hygroscopic, requires periodic replacement)
Power Steering Fluid:
Automatic Transmission Fluid (ATF) or specific hydraulic fluid as per manual.
Differential Oil:
EP 90 gear oil (or specified grade)
Engine:
Overheating due to undersized original radiators, camshaft wear, timing chain stretch.
Chassis:
Rust in sills, rear wheel arches, boot floor, and suspension mounting points.
Electrical:
Lucas electrical components can be prone to issues; aging wiring looms.
Suspension:
Wear in bushes and ball joints, potential for steering box leaks.
Typical Filter Oil:
e.g., Fram PH8A or equivalent (ensure correct fitment)
Heritage:
Jaguar Cars is renowned for its sporting heritage, elegant design, and performance-oriented luxury vehicles.
Mark X Development:
Developed from the Jaguar Mark IX, it represented a significant advancement in Jaguar's large saloon offering, featuring a new monocoque chassis construction and independent rear suspension.
Series Distinction:
The Mark X (Series 1) initially featured the 3.8L engine. The 4.2L engine was introduced with the Series 2, and the model was eventually renamed the 420G to align with Jaguar's naming conventions and differentiate it from the smaller Jaguar 420.
Manufacturing Location:
Coventry, England
Production Numbers:
Total production for Mark X and 420G combined is approximately 11,209 units.
