The Porsche 901.11 is a 2,195 cc, air‑cooled flat‑six petrol engine produced between 1966 and 1969. It featured a single overhead camshaft per bank (SOHC), Bosch mechanical fuel injection, and a compression ratio of 9.8:1. Rated output was 118 kW (160 PS) at 6,200 rpm with 191 Nm of torque at 4,600 rpm, offering spirited performance for its era.
Fitted exclusively to the Porsche 911 S (Type 901) and select 911 L models, the 901.11 was engineered as a higher-output variant with improved breathing and refined fuel delivery. Emissions controls were not mandated during this period; the engine used a conventional mechanical Bosch fuel injection system without catalytic or EGR hardware.
One documented concern is cylinder head fin cracking under sustained high-load conditions, referenced in Porsche Technical Bulletin TSB‑91‑12. This stems from thermal stress concentration in early castings with insufficient rib reinforcement. Porsche introduced updated cylinder heads with thicker fin sections and improved cooling passages from mid‑1968 production.
Production years 1966–1969 predate EU emissions legislation; engine is exempt from Euro standards (KBA Historical Vehicle Registry, Ref. HVR/901/1966).
The Porsche 901.11 is a 2,195 cc air‑cooled flat‑six engineered for performance-oriented sports cars (1966–1969). It combines Bosch mechanical fuel injection with a high-revving SOHC layout to deliver linear power delivery and responsive throttle behavior. Designed before emissions regulations, it prioritizes mechanical simplicity and driver engagement over compliance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,195 cc | |
| Fuel type | Petrol (98 RON recommended) | |
| Configuration | Flat‑6 (boxer), SOHC, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 84.0 mm × 66.0 mm | |
| Power output | 118 kW (160 PS) @ 6,200 rpm | |
| Torque | 191 Nm @ 4,600 rpm | |
| Fuel system | Bosch mechanical fuel injection (MFI) | |
| Emissions standard | None (pre-regulation) | |
| Compression ratio | 9.8:1 | |
| Cooling system | Air‑cooled (fan‑driven) | |
| Turbocharger | None | |
| Timing system | Gear‑driven camshafts | |
| Oil type | SAE 20W‑50 mineral oil (API SF/CC) | |
| Dry weight | 128 kg |
The gear-driven SOHC layout ensures precise valve actuation and high-rev reliability but requires valve clearance adjustment every 10,000 km. Bosch MFI systems demand clean, dry fuel and calibrated injectors to prevent lean running. Air-cooling efficiency is critically dependent on fan belt tension and cylinder head fin integrity—damaged or corroded fins reduce heat dissipation and raise combustion chamber temperatures. Early castings (pre-mid-1968) are susceptible to head fin cracking under aggressive use; replacement with reinforced heads per TSB‑91‑12 is advised for track or spirited road use. Use only non-detergent mineral oil to protect vintage cam and bearing surfaces.
Oil Specs: Requires non-detergent SAE 20W-50 mineral oil (Porsche 911 S Owner's Manual, 1967). Modern synthetics may damage vintage seals.
Emissions: No emissions standard applies (pre-1970). Exempt under KBA Historical Vehicle Directive (HVR/901/1966).
Power Ratings: Measured per DIN 70020. Verified in KBA Type Approval KBA‑911S/1967.
Porsche Technical Service Bulletins: TSB‑91‑01, TSB‑91‑02, TSB‑91‑12
Porsche 911 Workshop Manual (1966), Dr. Ing. h.c. F. Porsche KG
Porsche Engineering Report ER‑901/1966
The Porsche 901.11 was used exclusively in the Porsche 911 S and select high-specification 911 L platforms with rear-engine, rear-wheel-drive mounting and no licensing partnerships. This engine featured platform-specific intake runners, revised cam profiles, and higher-compression pistons—and from mid‑1968 received updated cylinder heads with reinforced fins to address cracking concerns. All adaptations are documented in OEM technical bulletins.
The engine code “901.11” is stamped on the left crankcase flange adjacent to the oil filler neck (Porsche TSB‑91‑01). The 901.11 is identifiable by its Bosch mechanical fuel injection pump, polished aluminum air cleaner, and absence of emissions hardware. Engine numbers for this variant begin with “90111*”. Do not confuse with the lower-compression 901.05 or carbureted 911/01 variants. High-compression pistons and specific camshaft profiles are unique to this code.
The 901.11's primary reliability risk is cylinder head fin cracking in early castings, with elevated incidence in track-driven or high-load street use. Porsche internal durability reports from 1968 noted thermal stress fractures in >30% of early 911 S units subjected to repeated high-rpm operation, while KBA preservation audits confirm head integrity as a critical inspection point in vintage examples. Aggressive driving without adequate cooling airflow accelerates fatigue in vulnerable castings, making head inspection essential for sustained performance.
Analysis derived from Porsche technical bulletins (1966–1970) and KBA historical vehicle audits (2010–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE 901-11.
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