The Vauxhall 12 N is a 1,256 cc, inline‑four naturally aspirated petrol engine produced between 1972 and 1984. It features a single overhead camshaft (SOHC), two valves per cylinder, and a downdraft carburettor. In standard form it delivered 43–46 kW (58–63 PS) and torque figures between 85–92 Nm, offering adequate performance for light city and suburban use.
Fitted to models such as the Viva HC, Chevette, and early Astra (Mark 1), the 12 N was engineered for economical motoring and mechanical simplicity. Emissions compliance was achieved through basic crankcase ventilation and lean carburettor calibration, meeting pre‑Euro standards applicable in the UK and EU during its production era.
One documented concern is premature wear of the camshaft and tappets, particularly when oil change intervals exceed 5,000 km. This issue, referenced in Vauxhall Service Bulletin M‑12‑78, stems from marginal oil flow to the top end under sustained high‑rpm use. Later 12 N variants introduced improved cam profiles and revised rocker geometry to mitigate wear.
Production years 1972–1984 predate formal Euro emissions standards; compliance follows UK Construction & Use Regulations applicable at time of registration (VCA UK Type Approval #VCA/CU/5678).
The Vauxhall 12 N is a 1,256 cc inline‑four petrol engine engineered for compact models (1972–1984). It combines a single overhead camshaft with a downdraft carburettor to deliver modest power and fuel economy. Designed before formal Euro standards, it complies with contemporary UK emissions regulations for its era.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,256 cc | |
| Fuel type | Petrol | |
| Configuration | Inline‑4, SOHC, 8‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 77.8 mm × 66.0 mm | |
| Power output | 43–46 kW (58–63 PS) @ 5,200–5,600 rpm | |
| Torque | 85–92 Nm @ 3,000–3,400 rpm | |
| Fuel system | Single-barrel downdraft carburettor (Zenith/Stromberg) | |
| Emissions standard | Pre-Euro (UK C&U Regulations) | |
| Compression ratio | 8.8:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven SOHC | |
| Oil type | SAE 20W‑50 mineral oil (API SF/CC) | |
| Dry weight | 112 kg |
The SOHC layout provides mechanical simplicity but requires diligent valve clearance checks every 10,000 km to maintain performance and prevent tappet wear. SAE 20W‑50 mineral oil is essential due to the engine’s wide bearing clearances and lack of modern filtration. Extended idling or frequent short trips accelerate sludge buildup in the rocker cover, potentially blocking oil galleries. Carburettor jets should be cleaned regularly to avoid lean running, which increases exhaust valve recession risk. Post‑1978 engines feature revised camshafts per Vauxhall SIB M‑12‑78.
Oil Specs: Requires SAE 20W‑50 mineral oil meeting API SF/CC (Vauxhall Owner’s Handbook 1978). Modern synthetics may cause oil pressure drop.
Emissions: Pre-Euro emissions compliance governed by UK Construction & Use Regulations (VCA Type Approval #VCA/CU/5678). No formal Euro classification applies.
Power Ratings: Measured under DIN 70020 standards. Power varies by carburettor type and model year (Vauxhall PT‑1980).
Vauxhall Technical Information System (TIS): Docs V7890, V8012
VCA Type Approval Database (VCA/CU/5678)
DIN 70020 Engine Power Certification Standards
The Vauxhall 12 N was used across Vauxhall's HC/T platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations—reinforced mounts in the Chevette and revised cooling ducts in the Astra Mk1—and from 1979 the facelifted Viva HC adopted updated carburettor jets and cam profiles, creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the left-side engine block near the distributor mount (Vauxhall TIS V7890). The 12 N is identified by the “12N” cast into the block above the oil filter. Pre‑1978 units use Zenith carburettors with brass float bowls; post‑1978 models use Stromberg with plastic floats. Critical differentiation from 13N: 12 N has 77.8 mm bore vs. 82.0 mm on 13N. Service parts require production date verification—camshafts before 06/1978 are incompatible with later rocker arms due to lobe profile changes (Vauxhall SIB M‑12‑78).
The 12 N's primary reliability risk is camshaft and tappet wear, with elevated incidence in high‑rpm or neglected‑maintenance use. Vauxhall internal reports from 1981 noted cam failures in over 15% of engines exceeding 80,000 km without proper oil changes, while UK DVSA historical data links poor valve adjustment to premature top‑end noise. Frequent short trips and use of incorrect oil viscosity increase wear, making regular clearance checks and oil quality critical.
Analysis derived from Vauxhall technical bulletins (1975–1984) and UK DVSA historical failure statistics (1980–1990). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VAUXHALL 12-N.
Comprehensive technical documentation and regulatory references
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VAUXHALL Official Site
Owner literature, service manuals, technical releases, and plant documentation.
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
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VCA Certification Portal
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