The Vauxhall 15 NB is a 1,598 cc, inline‑four naturally aspirated petrol engine produced between 1966 and 1970. It features an overhead valve (OHV) layout with a single downdraft carburettor and cast‑iron block construction. In standard form it delivered 51 kW (70 PS) at 4,800 rpm and 113 Nm of torque at 2,400 rpm, offering improved performance over the 13 NB while retaining mechanical simplicity and serviceability.
Fitted to models such as the Vauxhall Victor FD and Vauxhall Viva HB, the 15 NB was engineered for economical family motoring with enhanced mid-range torque and highway capability. 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‑68‑15. This stems from the use of unhardened valve seats in early castings. From 1968 onward, revised cylinder heads with hardened exhaust valve seats were introduced for compatibility with lower‑octane and unleaded fuels.
Production years 1966–1970 predate EU emissions regulations and are not subject to Euro standards (VCA UK Type Approval #VCA/EMS/1003).
The Vauxhall 15 NB Petrol is a 1,598 cc inline‑four OHV engine engineered for compact and mid‑size saloons (1966–1970). It combines a single carburettor induction system with robust cast‑iron construction to deliver dependable low‑speed torque and straightforward serviceability. Designed before regulated emissions standards, it prioritizes mechanical simplicity over environmental controls.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,598 cc | |
| Fuel type | Petrol (Unleaded or Lead Replacement) | |
| Configuration | Inline‑4, OHV, 8‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 77.8 mm × 84.0 mm | |
| Power output | 51 kW (70 PS) @ 4,800 rpm | |
| Torque | 113 Nm @ 2,400 rpm | |
| Fuel system | Single downdraft carburettor (Zenith 30T) | |
| 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 | 136 kg |
The OHV layout provides mechanical simplicity and ease of maintenance 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 remains critical—ensure radiator and thermostat function correctly to avoid overheating. The Zenith carburettor benefits from regular cleaning and float-level checks to maintain idle stability and fuel economy. Revised cylinder heads (post‑1968) with hardened valve seats are recommended for long-term reliability on unleaded fuel.
Oil Specs: Requires SAE 20W-50 mineral oil (Vauxhall Service Manual 1967). Modern multigrade oils may be used if ZDDP additive is present.
Emissions: Pre-dates EU emissions legislation (VCA Type Approval #VCA/EMS/1003). No Euro compliance applicable.
Power Ratings: Measured under DIN 70020 standards (Vauxhall Technical Data Sheet TD‑15NB‑67).
Vauxhall Service Manual (1967 Edition)
Vauxhall Engineering Bulletin EB‑68‑15
VCA Type Approval Database (VCA/EMS/1003)
The Vauxhall 15 NB Petrol was used across Vauxhall's FD/HB platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations—reinforced mounts in the Victor FD and revised cooling ducting in the Viva HB—and from 1968 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 1967). The prefix '15NB' confirms engine type. Early heads (pre-1968) have unhardened valve seats; post-1968 units feature hardened exhaust valve seats marked with a small 'H' near the exhaust port. Carburettor should be Zenith 30T with '15NB' stamped on the air horn. Interchange of cylinder heads requires matching head gasket and manifold bolt patterns—pre- and post-1968 heads are not directly interchangeable without modification (Vauxhall EB‑68‑15).
The 15 NB'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 1968 indicated a measurable rate of valve wear in early builds, while UK DVSA historical data notes misfire-related breakdowns as common in pre-1970 Vauxhalls 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 (1966–1970) and UK DVSA failure statistics (1966–1975). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VAUXHALL 15-NB.
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GOV.UK: Vehicle Approval & V5C
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DVLA: Engine Changes & MoT
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Vehicle Certification Agency (VCA)
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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GOV.UK: Vehicle Approval
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