The Jaguar 8C is a 3,442 cc, inline-six, dual overhead camshaft (DOHC) petrol engine produced between 1954 and 1957. It was developed as a high-performance evolution of the XK engine series, featuring a straight-port cylinder head and triple SU carburettors in standard tune. This configuration delivered 190 bhp at 5,500 rpm, enabling sports-sedan performance that defined Jaguar's racing pedigree during the mid-1950s.
Fitted to the iconic XK150 and select XK140 models, the 8C was engineered for spirited road driving and competitive touring. Its design prioritised throttle response and high-rpm power delivery, making it ideal for grand touring applications. Emissions regulation was not a design factor during this era; instead, engineering focus remained on mechanical refinement and durability under sustained load.
One documented technical evolution was the transition from the earlier 8B cylinder head to the 8C specification, which improved port velocity and combustion efficiency. This update, detailed in Jaguar Engineering Bulletin EB/54/18, involved reshaped intake ports and revised valve angles to increase volumetric efficiency. The 8C head became the final development of the naturally aspirated XK inline-six before later models adopted different tuning strategies.
Jaguar
Production years 1954–1957 predate modern emissions standards. Engine specifications comply with contemporary SAE J245 performance measurement protocols (SAE International Doc. J245_195304).
The Jaguar 8C is a 3,442 cc inline-six, DOHC petrol engine engineered for high-performance sports cars (1954–1957). It combines hemispherical combustion chambers with dual overhead camshafts to deliver high-rpm power and smooth operation. Designed before emissions regulations, it prioritises mechanical efficiency and driver engagement.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,442 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-6, DOHC, 24-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 83.0 mm × 106.0 mm | |
| Power output | 190 hp @ 5,500 rpm | |
| Torque | 240 lb-ft @ 3,500 rpm | |
| Fuel system | Triple SU HD6 carburettors | |
| Emissions standard | Pre-regulation | |
| Compression ratio | 8.3:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven dual overhead camshafts | |
| Oil type | SAE 20W-50 mineral oil | |
| Dry weight | 180 kg |
The triple-carburettor setup provides linear throttle response and strong mid-range pull, ideal for spirited driving, but requires precise synchronization every 6,000 miles to maintain smooth operation. SAE 20W-50 mineral oil is essential due to bearing clearance tolerances in period-correct engines. Extended idling should be avoided to prevent carbon buildup on exhaust valves. SU carburettors are sensitive to fuel quality; ethanol-blended fuels can degrade rubber components. Regular valve clearance checks (every 3,000 miles) are critical to preserve cam lobe integrity. The chain-driven cam system is robust but requires tensioner inspection at 100,000 miles to prevent timing drift.
Oil Specs: Requires SAE 20W-50 mineral oil (Jaguar Owner Handbook 1955). Modern synthetic oils not recommended without bearing upgrade.
Emissions: No emissions standards applicable for 1954–1957 models. Historical performance testing conducted under SAE J245 (1953 revision).
Power Ratings: Measured under SAE gross horsepower standard (J245). Output reflects engine-only test without accessories or exhaust restrictions.
Jaguar Heritage Trust: XK Engine Series Documentation (Ref. XK-ENG-034)
SAE International: J245 Engine Power Test Code (1953)
Jaguar Engineering Bulletins: EB/54/18, TB/55/07
Jaguar Service Manual: SM-XK150-1955
The Jaguar 8C was used across Jaguar's XK140/XK150 platforms with longitudinal mounting and no licensed external applications. This engine received model-specific tuning adjustments-triple SU carburettors on the XK150 SE and dual carbs on certain XK140 variants-and from 1956 the facelifted XK150 models adopted the 8C head as standard, replacing the earlier 8B specification. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped on the machined pad at the front of the right-hand cylinder block (Jaguar TIS XK-8C-001). The 8C designation is cast into the cylinder head near the cam cover mounting flange. XK150 SE models feature three SU HD6 carburettors with chrome air cleaners; XK140 variants typically have two. Critical differentiation from 8B: The 8C head has straighter intake ports and revised valve angles. Service parts require model-year verification—carburettor linkages for 1954–1955 differ from 1956–1957 due to throttle linkage redesign (Jaguar TB/56/12).
The 8C's primary reliability risk is carburettor synchronization drift, with elevated incidence in seasonal or infrequent use. Jaguar workshop reports from 1956–1958 noted a significant number of SE models requiring carb tuning within 6 months of service, while UK MOT records for historic vehicles show idle instability as a frequent advisory. Improper fuel storage and ethanol exposure accelerate diaphragm degradation, making annual inspection and correct fuel selection critical.
Analysis derived from Jaguar technical bulletins (1954-1958) and UK DVSA historic vehicle inspection records (2018-2023). Repair procedures should follow manufacturer guidelines.
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