The Vauxhall 25 SV is a 2,490 cc, inline‑six naturally aspirated petrol engine produced between 1979 and 1986. It features an overhead camshaft (OHC) layout with a single downdraft carburettor and a cast‑iron block with an aluminium alloy head. In standard form it delivered 85–95 kW (115–129 PS) and 185–205 Nm of torque, offering smooth power delivery and refined performance for executive applications.
Fitted to models such as the Carlton Mk2, Senator Mk1, and Viceroy, t…
Production years 1979–1986 predate formal Euro emissions standards; compliance limited to national regulations of the era .
The Vauxhall 25 SV is a 2,490 cc inline‑six OHC petrol engine engineered for executive models (1979–1986). It combines a single carburettor with a durable cast‑iron block to deliver smooth, linear power and refined drivability. Designed before formal Euro emissions regimes, it meets only national standards of its production era.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,490 cc | |
Fuel type | Petrol (lead or unleaded with modifications) | |
Configuration | Inline‑6, OHC, 12‑valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 88.0 mm × 91.0 mm | |
Power output | 85–95 kW (115–129 PS) @ 5,000–5,400 rpm | |
Torque | 185–205 Nm @ 2,800–3,200 rpm | |
Fuel system | Single downdraft carburettor (Zenith/Stromberg) | |
Emissions standard | Pre‑Euro (national standards only) | |
Compression ratio | 9.0:1 | |
Cooling system | Water‑cooled | |
Turbocharger | None | |
Timing system | Chain‑driven overhead camshaft (front‑mounted) | |
Oil type | SAE 20W‑50 mineral oil (API SF/CC) | |
Dry weight | 148 kg |
The Vauxhall 25 SV was used across Vauxhall's Senator and Carlton platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations—revised coolant routing in the Carlton Mk2 and altered exhaust manifolds in the Senator Mk1—and from 1984 the Viceroy adopted a modified sump and distributor bracket, creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
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Field reports and technical service bulletins highlight component wear patterns under high-load operation. Adherence to manufacturer service intervals and approved fluid specifications is critical for long-term reliability.
Analysis derived from manufacturer technical service bulletins and industry workshop records. Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
The 25 SV is generally robust if maintained properly, but pre-1984 versions are susceptible to camshaft wear under high-RPM use or extended oil intervals. Post-1984 models with hardened camshafts are more durable. Regular oil changes, clean fuel, and correct valve clearances help ensure longevity beyond 150,000 km.
Top issues include camshaft lobe wear (pre-1984), carburettor flooding or jetting issues, timing chain stretch, and coolant leaks from the water pump or manifold. These are documented in Vauxhall service bulletins and workshop manuals from the early–mid 1980s.
The 25 SV powered the Carlton Mk2 (1982–1986), Senator Mk1 (1979–1986), and Viceroy (1980–1984) in 2.5L form. It was never used in commercial vehicles or licensed to other manufacturers. All applications used longitudinal mounting in rear-wheel drive layouts.
Modest gains are possible: performance camshafts, twin-choke carburettors, or ported manifolds can raise output to ~105 kW. However, the OHC inline‑six design limits high-RPM potential compared to modern DOHC units. Most owners prioritize smoothness and reliability over tuning due to the engine’s vintage and parts availability.
Typical consumption is 11.0–12.5 L/100km (23–26 mpg UK) in mixed driving. Highway cruising can achieve 9.2 L/100km (31 mpg UK), while city use may exceed 14 L/100km. Economy depends heavily on carburettor condition and driving style.
No. The 25 SV is a non-interference OHC engine. If the timing chain fails, the pistons will not contact the valves, preventing catastrophic internal damage. This design enhances reliability in timing system failures.
Vauxhall specifies SAE 20W-50 mineral oil meeting API SF/CC standards. Modern synthetics are not recommended for original-spec engines due to potential seal incompatibility and tappet noise. Change every 8,000–10,000 km or annually.
Comprehensive technical documentation and regulatory references
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Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
Type-approval guidance and documentation.
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