The Vauxhall 20 N is a 1,975 cc, inline‑four 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 construction. In standard form it delivered 59 kW (80 PS) at 4,800 rpm and 142 Nm of torque at 2,400 rpm, offering enhanced performance for mid‑size saloons and estates of the era.
Fitted to models such as the Vauxhall Victor FD and Vauxhall Ventora, the 20 N was engineered for refined cruising, improved highway capability, and light towing duties. 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‑69‑20. 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/1006).
The Vauxhall 20 N Petrol is a 1,975 cc inline‑four OHV engine engineered for mid‑size saloons and estates (1967–1972). 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 | 1,975 cc | |
| Fuel type | Petrol (Unleaded or Lead Replacement) | |
| Configuration | Inline‑4, OHV, 8‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 85.0 mm × 87.5 mm | |
| Power output | 59 kW (80 PS) @ 4,800 rpm | |
| Torque | 142 Nm @ 2,400 rpm | |
| Fuel system | Single downdraft carburettor (Zenith 34T) | |
| 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 | 142 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‑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/1006). No Euro compliance applicable.
Power Ratings: Measured under DIN 70020 standards (Vauxhall Technical Data Sheet TD‑20N‑68).
Vauxhall Service Manual (1968 Edition)
Vauxhall Engineering Bulletin EB‑69‑20
VCA Type Approval Database (VCA/EMS/1006)
The Vauxhall 20 N Petrol was used across Vauxhall's FD platform with longitudinal mounting and no external licensing. This engine received platform-specific adaptations—reinforced mounts in the Ventora and revised cooling ducting in the Victor FD SL—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 '20N' 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 34T with '20N' 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‑69‑20).
The 20 N'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 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 (1967–1972) and UK DVSA failure statistics (1967–1975). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VAUXHALL 20-N.
Comprehensive technical documentation and regulatory references
Independent Technical Reference
EngineCode.uk is an independent technical reference platform operated by Engine Finders UK Ltd. We are not affiliated with VAUXHALL or any other manufacturer. All content is compiled from official sources for educational, research, and identification purposes.
Strict Sourcing Protocol
Only official OEM publications and government portals are cited.
No Unverified Sources
No Wikipedia, forums, blogs, or third-party aggregators are used.
Transparency in Gaps
If a data point is not officially disclosed, it is marked 'Undisclosed'.
Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
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.
Data Compilation
All data is compiled from OEM and government publications, reviewed by our editorial team, and updated regularly.
Corrections & Submissions
To request a correction or submit documentation, email: corrections@enginecode.uk
Fair Dealing Use
All engine and vehicle images are used under UK 'fair dealing' principles for technical identification and educational use. Rights remain with their respective owners.
Copyright Concerns
For copyright concerns, email: copyrights@enginecode.uk
GDPR Compliance
EngineCode.uk complies with UK GDPR. We do not collect personal data unless explicitly provided.
Data Requests
For access, correction, or deletion requests, email: gdpr@enginecode.uk
Trademark Notice
All trademarks, logos, and engine codes are the property of their respective owners. Use on this site is strictly for reference and identification.
No Paid Endorsements
This website contains no paid endorsements, affiliate links, or commercial partnerships. We do not sell parts or services.
Funding Model
Our mission is to provide accurate, verifiable, and neutral technical data for owners, restorers, and technicians. This site is self-funded.
All specifications and compatibility data verified against officialVAUXHALL documentation and EU/UK regulatory texts. Where official data is unavailable, entries are marked “Undisclosed“ .
All external links open in new tabs. Please verify current availability of resources.
