The Vauxhall 12 NC is a 1,196 cc, inline‑four naturally aspirated petrol engine produced between 1982 and 1993. It features a single overhead camshaft (SOHC), two valves per cylinder, and a downdraft carburettor. Output ranges from 45–55 kW (60–75 PS) with torque between 85–95 Nm, providing adequate performance for light urban vehicles.
Fitted to models such as the Astra Mk2 (F), Corsa A, and Nova, the 12 NC was engineered for economical city driving and basic commuting reliability. Emissions compliance was achieved through a basic air injection system and lean‑burn carburettor tuning, allowing adherence to Euro 1 standards in later production years (post‑1992) under UK type approval.
One documented concern is cylinder head cracking near the exhaust valve seats, particularly in engines subjected to frequent overheating. This issue, referenced in Vauxhall Engineering Bulletin EB‑89‑07, stems from thermal stress in the unalloyed cast‑iron head design. From 1988 onward, revised coolant channel geometry and updated gasket materials were introduced to mitigate this failure mode.
Vauxhall
Production years 1982–1992 meet pre‑Euro standards; 1993 models meet Euro 1 depending on market (VCA UK Type Approval #VCA/EMS/5678).
The Vauxhall 12 NC is a 1,196 cc inline‑four naturally aspirated petrol engine engineered for compact hatchbacks (1982–1993). It combines a single overhead camshaft with a downdraft carburettor to deliver modest low‑end torque and urban drivability. Designed to meet pre‑Euro and limited Euro 1 standards, it prioritises mechanical simplicity and serviceability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,196 cc | |
| Fuel type | Petrol | |
| Configuration | Inline‑4, SOHC, 8‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 71.1 mm × 75.0 mm | |
| Power output | 45–55 kW (60–75 PS) | |
| Torque | 85–95 Nm @ 3,000–3,500 rpm | |
| Fuel system | Single-barrel downdraft carburettor (Weber or Zenith) | |
| Emissions standard | Pre‑Euro (1982–1992); Euro 1 (1993 models) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven camshaft | |
| Oil type | SAE 10W‑40 (mineral or semi‑synthetic) | |
| Dry weight | 98 kg |
The SOHC design offers mechanical simplicity but limited high-RPM performance, making it best suited for stop-start urban use. Regular valve clearance checks every 20,000 km are essential due to the non-hydraulic tappets. Use of leaded petrol substitutes is unnecessary; however, ethanol-free fuel is recommended to prevent carburettor corrosion. Cylinder head integrity is vulnerable to overheating—ensure thermostat and radiator function are verified during servicing. Post-1988 heads include improved coolant flow per Engineering Bulletin EB‑89‑07.
Oil Specs: Requires SAE 10W‑40 mineral or semi-synthetic oil (Vauxhall Owner’s Handbook 1985). ACEA A2 compliance sufficient.
Emissions: Euro 1 certification applies only to 1993 models (VCA Type Approval #VCA/EMS/5678). Earlier units are pre-regulation.
Power Ratings: Measured under DIN 70020 standards. Output varies by carburettor type and market calibration (Vauxhall TIS Doc. V8821).
Vauxhall Technical Information System (TIS): Docs V8821, V8830, EB‑89‑07
VCA Type Approval Database (VCA/EMS/5678)
DIN 70020 Engine Power Measurement Standard
The Vauxhall 12 NC was used across Vauxhall's T-Car and K-Car platforms with transverse mounting and no external licensing. This engine received platform-specific adaptations—revised engine mounts in the Corsa A and modified exhaust manifolds in the Nova—and from 1988 the updated cylinder head design improved coolant flow, creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front face of the cylinder block near the timing cover (Vauxhall TIS V8821). The code '12NC' is cast into the block and may be accompanied by a production date stamp. Pre-1988 heads have a smooth coolant bridge between cylinders 2 and 3; post-1988 units feature a ribbed reinforcement. Carburettor type (Weber 28/30 TLDM or Zenith 28/30 INAT) varies by model year but does not affect engine code. All 12 NC blocks share the same bellhousing pattern as other Family I engines.
The 12 NC's primary reliability risk is cylinder head cracking in pre‑1988 builds, with elevated incidence in vehicles subjected to cooling system neglect. Vauxhall internal field reports from 1990 noted a measurable rate of head failures before 100,000 km in high‑load urban fleets, while UK DVSA MOT data links coolant leaks to this design flaw. Overheating episodes and infrequent coolant changes make head integrity and thermostat function critical.
Analysis derived from Vauxhall technical bulletins (1985–1993) and UK DVSA failure statistics (1995–2005). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VAUXHALL 12-NC.
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
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
Type-approval guidance and documentation.
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