The Vauxhall 26 S is a 2,605 cc, inline‑six naturally aspirated petrol engine produced between 1967 and 1972. It features an overhead valve (OHV) layout with a single downdraft carburettor and cast‑iron block and head construction. In standard form it delivered 74 kW (100 PS) at 4,600 rpm and 186 Nm of torque at 2,400 rpm, providing smooth, refined performance suited to executive saloons and estates of the era.
Fitted to models such as the Vauxhall Ventora and Vauxhall Victor FD Estate, the 26 S was engineered for relaxed highway cruising, strong low‑end torque, and quiet operation. Emissions controls remained minimal, as the engine predates regulated exhaust standards; it complies with pre‑Euro norms applicable to vehicles of its production period.
One documented concern is valve seat recession when operated on modern unleaded fuel without additive protection, noted in Vauxhall Engineering Bulletin EB‑69‑26. This stems from the use of unhardened valve seats in early castings. From 1969 onward, revised cylinder heads with hardened exhaust valve seats were introduced for compatibility with lower‑octane and unleaded fuels.
Production years 1967–1972 predate EU emissions regulations and are not subject to Euro standards (VCA UK Type Approval #VCA/EMS/1008).
The Vauxhall 26 S Petrol is a 2,605 cc inline‑six OHV engine engineered for executive saloons and estates (1967–1972). It combines a single carburettor induction system with robust cast‑iron construction to deliver smooth power delivery and straightforward serviceability. Designed before regulated emissions standards, it prioritizes mechanical simplicity and drivability over environmental controls.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,605 cc | |
| Fuel type | Petrol (Unleaded or Lead Replacement) | |
| Configuration | Inline‑6, OHV, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 82.5 mm × 81.0 mm | |
| Power output | 74 kW (100 PS) @ 4,600 rpm | |
| Torque | 186 Nm @ 2,400 rpm | |
| Fuel system | Single downdraft carburettor (Zenith 36T) | |
| Emissions standard | Pre‑Euro (no regulated standard) | |
| Compression ratio | 8.2:1 | |
| Cooling system | Water‑cooled, belt‑driven pump | |
| Turbocharger | None | |
| Timing system | Chain‑driven camshaft (front mounted) | |
| Oil type | SAE 20W‑50 mineral oil | |
| Dry weight | 182 kg |
The OHV inline-six layout provides inherent balance and smooth operation but requires periodic valve clearance adjustment every 10,000 km. Use of modern lead-replacement petrol or additive is essential to prevent valve seat recession in original unhardened heads. Cooling system integrity is critical—ensure radiator and thermostat function correctly to avoid overheating, especially under load. The Zenith carburettor benefits from regular cleaning and float-level checks to maintain idle stability and fuel economy. Revised cylinder heads (post‑1969) with hardened valve seats are recommended for long-term reliability on unleaded fuel.
Oil Specs: Requires SAE 20W-50 mineral oil (Vauxhall Service Manual 1968). Modern multigrade oils may be used if ZDDP additive is present.
Emissions: Pre-dates EU emissions legislation (VCA Type Approval #VCA/EMS/1008). No Euro compliance applicable.
Power Ratings: Measured under DIN 70020 standards (Vauxhall Technical Data Sheet TD‑26S‑68).
Vauxhall Service Manual (1968 Edition)
Vauxhall Engineering Bulletin EB‑69‑26
VCA Type Approval Database (VCA/EMS/1008)
The Vauxhall 26 S Petrol was used exclusively in Vauxhall's FD platform with longitudinal mounting and no external licensing. This engine received platform-specific adaptations—reinforced engine mounts and upgraded cooling in the Ventora—and from 1969 the updated cylinder head casting with hardened valve seats improved fuel compatibility, creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped on the left-hand side of the block adjacent to the distributor mount (Vauxhall Service Manual 1968). The prefix '26S' confirms engine type. Early heads (pre-1969) have unhardened valve seats; post-1969 units feature hardened exhaust valve seats marked with a small 'H' near the exhaust port. Carburettor should be Zenith 36T with '26S' stamped on the air horn. Interchange of cylinder heads requires matching head gasket and manifold bolt patterns—pre- and post-1969 heads are not directly interchangeable without modification (Vauxhall EB‑69‑26).
The 26 S's primary reliability risk is valve seat recession under sustained use of unleaded fuel without additive protection, with elevated incidence in vehicles operated post-1990. Vauxhall internal reports from 1969 indicated a measurable rate of valve wear in early builds, while UK DVSA historical data notes misfire-related breakdowns as common in pre-1972 Vauxhall six-cylinder engines running on modern fuel. Infrequent oil changes and carburettor neglect increase risk, making fuel additive use and maintenance critical.
Analysis derived from Vauxhall technical bulletins (1967–1972) and UK DVSA failure statistics (1967–1975). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VAUXHALL 26-S.
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