Jaguar XJ Series 1Saloon1968–1973

Jaguar XJ Series 1 Engines - The Complete UK Guide

Every engine fitted to the original XJ - from the 2.8-litre and 4.2-litre XK straight-sixes to the 5.3-litre V12 that arrived in 1972. Real UK costs and honest reliability data for the saloon that defined a generation. Backed by real UK enquiries in 2025 [EM-VERIFIED].

Explore XJ Series 1 Engines
151+XJ Series 1 Enquiries (2025)*
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Jaguar XJ Series 1 Engine Codes -
The Complete Database

Every engine fitted to the first‑generation XJ (Series 1) specifically - from the September 1968 launch to the 1973 end of production.

Engine CodeFuelPowerYearsReliabilityEnquiriesAvg. Recon Cost
7G (engine no. 7G.1001+)XK I6 2.8LPetrol, carburettor149 bhp / 104 kW1968–1973★★★☆☆ [PROVISIONAL - pending dedicated Engine Page][PATTERN DATA]£3,500–£6,000 [EM-QUOTE]
7L (engine no. 7L.1001+)XK I6 4.2LPetrol, carburettor173 bhp / 129 kW1968–1973★★★★☆ [PROVISIONAL - pending dedicated Engine Page][PATTERN DATA]£4,500–£8,000 [EM-QUOTE]
-XK I6 3.4LPetrol, carburettor162 bhp1972–1973 (late Series 1, some markets)★★★½☆ [PROVISIONAL - pending dedicated Engine Page][PATTERN DATA]£4,000–£7,000 [EM-QUOTE]
-V12 5.3LPetrol, carburettor251 bhp / 187 kW1972–1973★★★☆☆ [PROVISIONAL - pending dedicated Engine Page][PATTERN DATA]£6,000–£12,000 [EM-QUOTE]
BMW 3 Series E90

Overview

Jaguar XJ Series 1 - Overview

The XJ Series 1 is the original Jaguar XJ, launched in September 1968 as the successor to a confusing range of Jaguar saloons - the 420, 420G and S‑Type.

Designed under the direction of Sir William Lyons, it was intended to be the definitive Jaguar saloon: combining E‑Type‑inspired styling, superb ride quality, and exceptional performance. The XJ6 launched with a choice of 2.8‑litre or 4.2‑litre versions of Jaguar's legendary XK straight‑six engine. In 1972, a long‑wheelbase option was introduced, followed in March 1973 by the V12‑powered XJ12. Production of the Series 1 ran until 1973, when it was replaced by the Series 2.

Key Facts

Platform

Monocoque with independent rear suspension

Predecessor

Jaguar 420 / 420G / S‑Type

Successor

XJ Series 2

Sibling body styles in this generation

None (4‑door saloon only; Daimler Sovereign variants were badge‑engineered versions)

Market Intelligence

The XJ Series 1 generates consistent UK enquiries [PATTERN DATA], concentrated on 4.2‑litre six‑cylinder cars as these classics enter collector and restoration territory.

Best & Worst Engines

Thin-Data Summary

“Most dependable: The 4.2‑litre XK straight‑six (7L) - a development of the legendary E‑Type engine - offers the best balance of power, refinement and reliability in the Series 1 range, with a proven 200,000‑mile capability when properly maintained. The 2.8‑litre XK six is underpowered for the XJ's weight and less reliable; the 5.3‑litre V12 is a glorious powerhouse but complex, costly to maintain, and best left to specialist care. The late‑run 3.4‑litre six is a rare and solid middle ground. Buyers should prioritise a well‑maintained 4.2 with documented service history.”

Who it's for:

Jaguar XJ Series 1
Ownership Economics

EngineTypical MileageCommon Major FailureRepair Cost (Specialist)Replacement Cost (Recon)Ownership Verdict
2.8 XK I660k–120kHead gasket, carburettor issues£500–£1,500£3,500–£6,000
Underpowered - smooth but under‑spec'd for the XJ
4.2 XK I6100k–200kCooling system, timing chain, head gasket£400–£1,500£4,500–£8,000
Best Six - the XJ's most complete engine
3.4 XK I680k–150kCooling system, carburettor wear£500–£1,500£4,000–£7,000
Rare Middle Ground - solid but uncommon
5.3 V1260k–120kCooling system, ignition, carburettor balance£800–£2,500£6,000–£12,000
Most Expensive - glorious but costly to maintain

The XJ Series 1 rule

A £4,500–£8,000 4.2 recon against a £5,000–£20,000 Series 1 XJ sits at 22–160% of the car's value. On a sub‑£7,000 example, that brushes our 60% Jaguar threshold - we'll honestly tell you to walk away. Against a well‑kept £15,000+ example, the same recon drops to a routine 30–53% - a repair decision, not a financial one. Value the car first.

Common Problems

XK Six Cooling System Failure (4.2 & 3.4)
5.3 V12 Ignition & Carburettor Balance
2.8 XK Six Head Gasket & Carburettor Wear
XJ Series 1 Body & Chassis Corrosion (Non‑Engine)

XJ Series 1
Engine Replacement Costs - By Engine and Condition

No Generation variance from the Model Page's baseline figures - XJ Series 1 saloon shares identical engine‑bay access across all variants, so costs are inherited directly per the Authority Model, with no divergence note required. All costs are [EM-QUOTE] from Table A - Engine Replacement Economics (classic engine costs estimated from specialist supplier data).

Diesel & Petrol Lineup

Petrol Variants

Scope note: All variants listed are Jaguar XJ Series 1 (1968–1973) only - 4‑door saloon body style. Daimler Sovereign variants were virtually identical to the Jaguar‑badged cars and share the same engine line‑up. Series 2 (1973–1979) is covered on its own Generation Page.

Market Intelligence

Most Requested Engines (2025)

    Most Requested Variants

      Average Replacement Cost

      Most Common Failures

        Frequently Asked Questions

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