The Porsche 911.04 is a 1,991 cc, flat‑six (horizontally opposed) naturally aspirated petrol engine produced between 1966 and 1967. It powered the base — model Porsche 911, serving as the production successor to the short — lived 901.01 after Peugeot’s naming objection. Featuring an air‑cooled design, single overhead camshafts per bank (SOHC), and dual carburetors (Solex 40 PII — 4), it delivered 110 PS (81 kW) at 6,000 rpm and 158 Nm of torque. This engine prioritized mec…
The 911.04 predates EU emissions regulations and was not type-approved under modern frameworks (VCA/EU).
The Porsche 911.04 is a 1,991 cc flat‑six air‑cooled petrol engine engineered for entry-level sports coupés (1966–1967). It combines SOHC valvetrain architecture with twin Solex carburetors to deliver responsive throttle response and accessible performance. Designed before emissions regulation, it prioritizes mechanical reliability and driver engagement.
| Parameter | Value | Source |
|---|---|---|
Displacement | 1,991 cc | |
Fuel type | Petrol (Gasoline) | |
Configuration | Flat‑6 (horizontally opposed), SOHC, 12‑valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 80.0 mm × 66.0 mm | |
Power output | 81 kW (110 PS) @ 6,000 rpm | |
Torque | 158 Nm @ 4,000 rpm | |
Fuel system | Twin Solex 40 PII-4 carburetors | |
Emissions standard | Not applicable (pre-regulation era) | |
Compression ratio | 9.0:1 | |
Cooling system | Air‑cooled (fan‑driven) | |
Turbocharger | None | |
Timing system | Chain-driven camshafts (dual chains) | |
Oil type | SAE 20W-50 mineral oil (API SC/SD) | |
Dry weight | 175 kg |
The Porsche 911.04 was used exclusively in the Porsche base-model 911 with rear‑engine, longitudinal mounting. This entry-level variant provided core 911 driving dynamics without the performance enhancements of the S or T models. No cross‑manufacturer or platform sharing occurred. All revisions are documented in Porsche engineering bulletins.
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The 911.04's primary reliability considerations are valve seat recession under unleaded fuel, carburetor imbalance, and timing chain tensioner wear. Porsche’s internal durability logs from 1967 showed good longevity under period-correct fuel and maintenance, but modern operation without upgrades increases wear risk. Cold-engine stress and ethanol-blended fuels accelerate gasket and carburetor degradation.
Analysis derived from Porsche technical bulletins (1966–1968) and EU historical vehicle documentation (2010–2023). 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 proper maintenance and leaded-fuel substitutes, the 911.04 is dependable for classic use. Its lower state of tune reduces stress versus high-output variants, but valve seat wear from unleaded fuel and carburetor sensitivity remain key risks. Restored examples with hardened seats and correct oil can offer decades of reliable service.
Top issues include valve seat recession from unleaded fuel, Solex carburetor imbalance or flooding, timing chain tensioner wear, and oil leaks from aged gaskets. These are well-documented in the 1966 Porsche 911 Workshop Manual and Classic department service notes.
Exclusively the 1966–1967 base-model Porsche 911 Coupe (non-S, non-T). Approximately 1,750 units were produced between chassis numbers 300250 and 301999 as the standard 911 offering during this period.
Yes. Common upgrades include 9.5:1 pistons, performance camshafts, and Weber 40 IDA carburetors, yielding ~130 PS. The stock bottom end is robust, but major tuning should include valve seat upgrades and oil system improvements to match increased output.
Typical consumption is ~11.5 L/100km (city) and ~8.5 L/100km (highway), or about 25–28 mpg UK combined. Fuel economy is secondary to driving experience, but the base 911 is more efficient than the contemporary 911S.
No. The 911.04 is a non-interference engine. If the timing chain fails, pistons and valves do not collide, minimizing catastrophic damage—though the engine will stall and require timing repair.
Porsche specified SAE 20W-50 mineral oil meeting API SC/SD in 1966. Modern equivalents must be zinc-rich (ZDDP >1200 ppm) to protect flat-tappet cams. Synthetic oils are not recommended unless the engine is modified.
Comprehensive technical documentation and regulatory references
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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.
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