The Porsche 911.51 is a 2,994 cc, air‑cooled flat‑six petrol engine produced between 1976 and 1977. It features overhead camshafts driven by an intermediate shaft, Bosch K — Jetronic mechanical fuel injection, and a dry‑sump lubrication system. In standard form it delivered 132 kW (180 PS) at 5,900 rpm and 250 Nm of torque at 4,200 rpm, offering increased displacement and torque over the 2.7L units.
Fitted exclusively to the Porsche 911 Carrera 3.0 in European and ROW marke…
The 911.51 predates EU emissions regulations; no Euro standard applies (VCA historical vehicle exemption class).
The Porsche 911.51 is a 2,994 cc air‑cooled flat‑six petrol engine engineered for the 911 Carrera 3.0 grand tourer (1976–1977). It combines Bosch K-Jetronic mechanical fuel injection with chain-driven overhead camshafts to deliver smooth power delivery and strong mid-range torque. Designed before formal emissions mandates, it prioritizes drivability and mechanical precision while meeting early national standards.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,994 cc | |
Fuel type | Petrol (min. 95 RON) | |
Configuration | Flat‑6 (Boxer), SOHC, 2 valves per cylinder | |
Aspiration | Naturally aspirated | |
Bore × stroke | 95.0 mm × 70.4 mm | |
Power output | 132 kW (180 PS) @ 5,900 rpm | |
Torque | 250 Nm @ 4,200 rpm | |
Fuel system | Bosch K-Jetronic mechanical fuel injection | |
Emissions standard | Not applicable (pre-regulation era) | |
Compression ratio | 8.5:1 | |
Cooling system | Air‑cooled (engine-driven fan) | |
Turbocharger | None | |
Timing system | Intermediate shaft with spur gears and chains | |
Oil type | SAE 20W‑50 mineral oil (API SN or equivalent) | |
Dry weight | 142 kg |
The Porsche 911.51 was used exclusively in the Porsche 911 Carrera 3.0 platform with rear‑mounted longitudinal orientation and no external licensing. This engine received model-specific adaptations—reinforced engine mounts and revised oil cooler routing in the Carrera 3.0—and from 1978 was replaced by the 930/60 turbocharged variant, creating a clear production boundary. All adaptations are documented in OEM technical bulletins.
Engine Finders UK Ltd, which operates EngineCode.uk, can pass your enquiry to engine suppliers in the UK. The service is for vehicles in the United Kingdom, with UK delivery or fitting. This is a commercially connected service, and sending an enquiry does not confirm diagnosis or compatibility.
Diagnostic reminder: If a technician has recommended replacing the engine, you can send an enquiry to engine suppliers in the UK. Confirm the diagnosis first: an engine-code record does not diagnose a fault.
The 911.51's primary reliability risk is intermediate shaft bearing wear under sustained high-RPM operation, with Porsche internal durability reports from 1977 indicating timing drift in 7–10% of engines before 60,000 km in performance use. The lack of updated bushings in this short-run model makes proactive maintenance critical. Infrequent oil changes and ethanol-blended fuels accelerate fuel system and valve train degradation, making oil quality and fuel selection essential.
Analysis derived from Porsche technical bulletins (1976–1977) and EU historical vehicle maintenance guidelines (2007–2023). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
With strict maintenance—especially frequent oil changes using ZDDP-rich 20W-50 oil—the 911.51 can be robust. However, as a short-production engine without the later bronze intermediate shaft bushings, it is prone to timing wear under high-RPM use. Avoid ethanol fuels and ensure proper warm-up to ensure longevity beyond 100,000 km.
Intermediate shaft wear, K-Jetronic regulator drift, rear main seal leaks, and cam lobe wear are the top concerns. These are documented in Porsche Technical Bulletin PTB‑92/76 and late-1970s 911 workshop manuals.
Exclusively the 911 Carrera 3.0 (1976–1977) in Coupé and Targa forms. It was not used in US-spec models (which received different 2.7L variants) or in the 930 Turbo, which used the 930/60 engine.
Yes. Common upgrades include higher-compression pistons (9.5:1), performance cams, and K-Jetronic recalibration. With these, 200–210 PS is achievable. However, intermediate shaft upgrades are strongly recommended before any high-RPM tuning due to the original bushing design.
Typical consumption is 13.2 L/100km (city) and 9.6 L/100km (highway), or about 21.5 mpg UK combined. Real-world efficiency depends heavily on driving style, but most owners report 20–23 mpg (UK) on mixed routes.
Yes. The 911.51 is an interference engine—valves and pistons occupy the same space at TDC. Timing gear or intermediate shaft failure can cause catastrophic valve-to-piston contact. Regular inspection of shaft wear is essential.
SAE 20W-50 mineral oil with ZDDP (zinc) additive, meeting API SN or classic-spec standards. Change every 5,000 km, especially if used for performance driving. Synthetic oils without ZDDP should be avoided.
Comprehensive technical documentation and regulatory references
EngineCode.uk is operated by Engine Finders UK Ltd. It provides engine-reference information and an optional commercial enquiry service. It is not an official manufacturer website. Check the record's sources and confirm vehicle-specific details before relying on it for parts, repairs or replacement.
Our editorial standard prioritises relevant manufacturer documentation and official regulatory sources. The sources and verification status for a record should be checked alongside the data.
A statement is not verified merely because a source is listed. Where supporting evidence is missing or conflicting, the record should identify that limitation. Please report unsupported or inconsistent information.
Transparency in gaps
A missing or unverified value does not mean the manufacturer has withheld it. We distinguish information not yet verified, information not available to us, and information explicitly not disclosed by the source.
Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
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.
Records are subject to review and correction. Source links, dates and verification notes should be read with the technical information. Our Editorial and Sourcing Policy explains our standards and review process.
Found an error or missing source? Report a problem with this page. Include the field or statement concerned and a supporting source if available. You can also email corrections@enginecode.uk.
Copyright and permissions
Images and other material may be protected by copyright. Attribution does not by itself grant permission to reuse material. If you believe material on this site infringes your rights, contact copyrights@enginecode.uk with the page URL and details of your claim. We will review the material and take appropriate action.
Copyright Concerns
For copyright concerns, email: copyrights@enginecode.uk
Our Privacy Policy explains how Engine Finders UK Ltd uses information from visits, vehicle lookups, enquiries and messages. Our Cookie Policy explains cookies and similar technologies and how to change your choices.
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.
Ownership and commercial services
EngineCode.uk is owned and operated by Engine Finders UK Ltd. Alongside our reference content, we offer an optional replacement-engine enquiry service through Engine Finders and may identify relevant services provided by businesses connected with us. These commercial connections are disclosed. Using an enquiry service is not required to read our reference content.
Engine Finders UK Ltd operates this website. Our optional enquiry service has a commercial purpose. Our Ownership and Commercial Disclosure explains the relationship between the reference website and that service. Participating suppliers pay a fee or subscription to participate on the network and receive quote requests.
Use this record as a starting point for identification. Specifications and vehicle applications may contain errors or omissions. Confirm the exact engine variant and compatibility using vehicle-specific documentation and a qualified supplier or technician.
All external links open in new tabs. Please verify current availability of resources.