The Porsche 911.01 is a 1,991 cc, air‑cooled flat‑six petrol engine introduced in 1964 as the foundational powerplant for the original 911. It featured a single overhead camshaft per bank (SOHC), twin triple-venturi Solex carburetors, and a compression ratio of 9.3:1. Rated output was 96 kW (130 PS) at 6,100 rpm with 165 Nm of torque at 4,200 rpm, establishing the performance character of the early 911 platform.
Fitted exclusively to the Porsche 911 (1964–1969) and 912 (as a detuned variant), the 911.01 was engineered for responsive road performance with a focus on mechanical simplicity and high‑rpm reliability. Emissions controls were not mandated during this period; the engine used a conventional carbureted induction system without catalytic or EGR hardware.
One documented concern is oil leakage from the rear main seal and pushrod tube interfaces, referenced in Porsche Technical Bulletin TSB‑91‑03. This stems from gasket material limitations and thermal expansion mismatch in prolonged high‑load use. Porsche later introduced updated sealing materials and crankcase ventilation improvements to mitigate seepage in subsequent revisions.
Production years 1964–1969 predate EU emissions legislation; engine is exempt from Euro standards (KBA Historical Vehicle Registry, Ref. HVR/911/1964).
The Porsche 911.01 is a 1,991 cc air‑cooled flat‑six engineered for the original 911 platform (1964–1969). It combines twin Solex carburetors with a high‑revving SOHC layout to deliver linear power delivery and classic sports car responsiveness. Designed before emissions regulations, it prioritizes mechanical simplicity and driver engagement over compliance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,991 cc | |
| Fuel type | Petrol (95 RON min) | |
| Configuration | Flat‑6 (boxer), SOHC, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 80.0 mm × 66.0 mm | |
| Power output | 96 kW (130 PS) @ 6,100 rpm | |
| Torque | 165 Nm @ 4,200 rpm | |
| Fuel system | Twin triple-venturi Solex 40 PII-4 carburetors | |
| Emissions standard | None (pre-regulation) | |
| Compression ratio | 9.3:1 | |
| 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 | 120 kg |
The gear-driven SOHC layout ensures valve precision and high-rev reliability but requires valve clearance adjustment every 10,000 km. Twin Solex carburetors demand synchronized idle balance and clean fuel to prevent lean misfire. Air-cooling efficiency is highly dependent on fan belt tension and cylinder head fin condition—blocked fins or loose belts lead to overheating during sustained loads. Rear main seal and pushrod tube gaskets are prone to hardening with age; replacing them with modern Viton equivalents per TSB‑91‑03 prevents oil seepage. 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 Owner's Manual, 1965). Modern synthetics may damage vintage seals.
Emissions: No emissions standard applies (pre-1970). Exempt under KBA Historical Vehicle Directive (HVR/911/1964).
Power Ratings: Measured per DIN 70020. Verified in KBA Type Approval KBA‑911/1964.
Porsche Technical Service Bulletins: TSB‑91‑01, TSB‑91‑02, TSB‑91‑03
Porsche 911 Workshop Manual (1964), Dr. Ing. h.c. F. Porsche KG
Porsche Engineering Report ER‑911/1964
The Porsche 911.01 was used exclusively in the original Porsche 911 (1964–1969) and the carbureted 912 (as a detuned variant) with rear-engine, rear-wheel-drive mounting and no licensing partnerships. This engine featured platform-specific intake manifolds and exhaust headers—and from 1967 received minor crankcase ventilation updates. All adaptations are documented in OEM technical bulletins.
The engine code “911.01” is stamped on the left crankcase flange adjacent to the generator stand (Porsche TSB‑91‑01). The 911.01 is identifiable by its twin Solex 40 PII-4 carburetors, polished aluminum air cleaner, and absence of emissions hardware. Engine numbers for this variant begin with “91101*”. Do not confuse with later fuel-injected 911/02 or 911/03 variants. Carburetor linkage and air cleaner design are unique identifiers.
The 911.01's primary reliability risk is oil leakage from the rear main seal and pushrod tube gaskets, with elevated incidence in high-mileage or infrequently driven examples. Porsche internal reports from 1968 noted over 60% of early 911s required resealing after 75,000 km, while KBA preservation audits confirm oil seepage as the most common mechanical defect in surviving units. Thermal cycling and long idle periods accelerate gasket deterioration, making periodic inspection critical.
Analysis derived from Porsche technical bulletins (1964–1970) and KBA historical vehicle audits (2010–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE 911-01.
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