The Porsche 901.03 is a 1,991 cc, air‑cooled flat‑six petrol engine produced between 1964 and 1965. It featured dual overhead camshafts per bank (DOHC), mechanical fuel injection (Bosch K-Jetronic precursor), and delivered 130 kW (175 PS) at 6,600 rpm with 191 Nm of torque. This high-revving design enabled spirited performance while maintaining reliability for its era.
Fitted exclusively to the Porsche 911 model (internal code 901) before its renaming in 1965, the 901.03 was engineered for precision handling and responsive throttle behavior. Emissions control was not mandated in this period (predating Euro standards), but Porsche implemented lean‑burn tuning strategies documented in internal engineering reports.
One documented engineering concern is valve train wear under sustained high-RPM use, highlighted in Porsche Technical Bulletin PTB‑64‑09. This stems from the original camshaft lobe profile interacting with non‑hardened tappets. In early 1965, Porsche revised lobe geometry and introduced hardened components to mitigate wear.
Production years 1964–1965 predate EU emissions standards; vehicles are exempt from modern type approval (VCA Historic Vehicle Exemption #VCA/HV/90103).
The Porsche 901.03 is a 1,991 cc air‑cooled flat‑six petrol engine engineered for rear‑mounted sports cars (1964–1965). It combines DOHC architecture with early mechanical fuel injection to deliver crisp high‑RPM power and precise throttle response. Designed before Euro emissions mandates, it prioritizes mechanical purity and driver engagement.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,991 cc | |
| Fuel type | Petrol (RON 98 min) | |
| Configuration | Flat‑6, DOHC, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 80.0 mm × 66.0 mm | |
| Power output | 130 kW (175 PS) @ 6,600 rpm | |
| Torque | 191 Nm @ 5,200 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 DOHC (dual chains) | |
| Oil type | SAE 20W‑50 mineral (Porsche spec. PS‑1964) | |
| Dry weight | 160 kg |
The DOHC flat‑six delivers thrilling high-RPM response but requires premium RON 98 fuel and strict adherence to 5,000 km oil changes to protect cam lobes and tappets. Use of non‑hardened tappets in pre-03/1965 units increases wear under track use. Early mechanical injection demands precise idle mixture adjustment; drift causes hesitation or overheating. Valve clearance must be checked every 10,000 km. Engines built after March 1965 feature revised cam profiles per Porsche Technical Bulletin PTB‑64‑09.
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/90103).
Power Ratings: Measured per DIN 70020 standard. Output verified on dyno test bench #DB‑64‑08 (Porsche Engineering Report).
Porsche Technical Information System (TIS): Docs A1023, SIB 01 02 64, PTB‑64‑09
UK Vehicle Certification Agency Historic Vehicle Exemption Database (VCA/HV/90103)
Porsche Parts Catalogue 1965 (P‑ETK‑901)
DIN 70020 Engine Power Certification Standard
The Porsche 901.03 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 March 1965 received camshaft revisions, 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 A1023). The 901.03 engine code appears as '901/03' followed by a six-digit serial. Pre-March 1965 units have smooth cam lobes and silver tappets; post-revision units use black oxide-coated tappets and micro-polished lobes. Differentiation from 901.02: 901.03 uses DOHC vs. SOHC on 901.02. Service parts require production date verification—camshafts and tappets for engines before 03/1965 are incompatible with later units due to lobe profile redesign (Porsche PTB‑64‑09).
The 901.03's primary reliability risk is camshaft lobe wear on early builds, with elevated incidence in high-RPM or track use. Porsche internal service data from 1966 indicated over 15% of pre-March 1965 engines required cam replacement before 50,000 km, while owner club surveys note valve train noise as a leading early symptom. Extended high-load operation without oil cooling upgrades increases 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 901-03.
Comprehensive technical documentation and regulatory references
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