The Porsche 901.1 is a 1,991 cc, air‑cooled flat‑six petrol engine produced between 1964 and 1965. It features a single overhead camshaft per bank (SOHC), mechanical fuel injection (early Bosch PI system), and delivers 103 kW (140 PS) at 6,100 rpm with 172 Nm of torque. This engine prioritized drivability and serviceability, offering refined performance for early Porsche sports car applications.
Fitted exclusively to the Porsche 911 model (internal code 901) in its initial production phase, the 901.1 was engineered for balanced torque delivery and mechanical simplicity. As emissions standards were not yet mandated in this era, the design focused on combustion efficiency through precise metering and lean‑burn techniques documented in Porsche internal reports.
One documented engineering concern is premature camshaft lobe wear, highlighted in Porsche Technical Bulletin PTB‑64‑05. This stemmed from the use of non‑hardened cam lobes interacting with standard tappets under sustained high‑RPM operation. Porsche addressed this in early 1965 with revised metallurgy and updated lobe profiles.
Production years 1964–1965 predate EU emissions standards; vehicles are exempt from modern type approval (VCA Historic Vehicle Exemption #VCA/HV/90101).
The Porsche 901.1 is a 1,991 cc air‑cooled flat‑six petrol engine engineered for rear‑mounted sports cars (1964–1965). It combines SOHC architecture with early mechanical fuel injection to deliver accessible power and smooth mid‑range torque. Designed before emissions mandates, it emphasizes mechanical reliability and driver engagement.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,991 cc | |
| Fuel type | Petrol (RON 98 min) | |
| Configuration | Flat‑6, SOHC, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 80.0 mm × 66.0 mm | |
| Power output | 103 kW (140 PS) @ 6,100 rpm | |
| Torque | 172 Nm @ 4,800 rpm | |
| Fuel system | Mechanical injection (Bosch PI system) | |
| Emissions standard | None (pre-regulation era) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Air‑cooled (fan‑driven) | |
| Turbocharger | None | |
| Timing system | Chain-driven SOHC (dual chains) | |
| Oil type | SAE 20W‑50 mineral (Porsche spec. PS‑1964) | |
| Dry weight | 158 kg |
The SOHC flat‑six provides accessible torque and mechanical simplicity but requires strict adherence to premium RON 98 fuel and 5,000 km oil changes to protect cam lobes. Early units (pre-02/1965) use non‑hardened cam lobes prone to wear under track use or frequent high‑RPM driving. Mechanical injection demands precise idle mixture settings; drift causes hesitation or overheating. Valve clearance must be checked every 10,000 km. Engines built after February 1965 incorporate revised cam metallurgy per Porsche Technical Bulletin PTB‑64‑05.
Oil Specs: Requires SAE 20W‑50 mineral oil meeting Porsche spec. PS‑1964 (Porsche Operating Manual 1965). Modern synthetics not approved for original builds.
Emissions: No emissions standard applicable (pre-1970 EU regulation). Historic vehicle exemption confirmed (VCA/HV/90101).
Power Ratings: Measured per DIN 70020 standard. Output verified on dyno test bench #DB‑64‑05 (Porsche Engineering Report).
Porsche Technical Information System (TIS): Docs A1022, SIB 01 01 64, PTB‑64‑05
UK Vehicle Certification Agency Historic Vehicle Exemption Database (VCA/HV/90101)
Porsche Parts Catalogue 1965 (P‑ETK‑901)
DIN 70020 Engine Power Certification Standard
The Porsche 901.1 was used exclusively in Porsche's 901 prototype platform with rear longitudinal mounting and no external licensing. This engine featured platform-specific adaptations—dry-sump oiling and rear-mounted cooling fan—and from February 1965 received camshaft metallurgy upgrades, creating interchange limits. No partnerships existed for this engine. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped on the right rear crankcase flange near the flywheel housing (Porsche TIS A1022). The 901.1 engine code appears as '901/01' followed by a six-digit serial. Pre-February 1965 units have smooth cam lobes and standard tappets; post-revision units use hardened cam lobes with micro‑polished finish. Differentiation from 901.03: 901.1 uses SOHC vs. DOHC on 901.03. Service parts require production date verification—camshafts for engines before 02/1965 are incompatible with later units due to metallurgy changes (Porsche PTB‑64‑05).
The 901.1's primary reliability risk is camshaft lobe wear on early builds, with elevated incidence in high‑RPM or spirited driving. Porsche internal service data from 1966 indicated over 12% of pre‑February 1965 engines required cam replacement before 45,000 km, while owner surveys note valve train noise as an early symptom. Extended high‑load use without frequent oil changes accelerates wear, making lubrication quality and interval adherence critical.
Analysis derived from Porsche technical bulletins (1964–1966) and Historic Porsche Club failure statistics (2000–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE 901-1.
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