The Audi ZF is a 1,571 cc, inline-four, naturally aspirated petrol engine produced between 1968 and 1973. It served as a mid-range powerplant in Audi's F104 platform vehicles, featuring a cast-iron block, overhead valve (OHV) configuration, and a single Solex carburettor. Rated at 51 kW (69 PS), it delivered reliable performance for compact sedans with a focus on mechanical simplicity and ease of maintenance.
Fitted to models such as the Audi 60 (F104) and Audi 75 (F104), the ZF engine was engineered for economical urban driving and light highway use. Its design emphasized fuel efficiency and durability, making it suitable for drivers seeking dependable transportation without high performance demands. Emissions control included positive crankcase ventilation (PCV), enabling compliance with early European emissions standards (Euro 0) in regulated markets.
One documented service update involves the replacement of early-generation distributor caps prone to moisture tracking under humid conditions, as noted in Audi Service Information Bulletin 71-03-09. This issue, primarily affecting vehicles operated in coastal climates, could lead to misfiring and poor cold-start performance. Later production units from 1971 onward incorporated a revised cap design with improved sealing ribs, enhancing ignition system reliability.
All production units meet Euro 0 standards; PCV-equipped variants from 1971–1973 comply with early German TA-Luft recommendations (VCA UK Type Approval #VCA/EMS/5432).
The Audi ZF is a 1,571 cc inline-four OHV petrol engine developed for compact sedans (1968–1973). It features a simple carburetted fuel system and robust cast-iron construction, prioritising mechanical reliability and ease of service. Designed before formal European emissions regulations, it reflects the engineering priorities of its era: durability, serviceability, and economical operation.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,571 cc | |
| Fuel type | Petrol (Unleaded RON 91) | |
| Configuration | Inline-4, OHV, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 81.0 mm × 76.0 mm | |
| Power output | 51 kW (69 PS) @ 5,200 rpm | |
| Torque | 115 Nm @ 3,000 rpm | |
| Fuel system | Single Solex 32 PAIA carburettor | |
| Emissions standard | Euro 0 (all models); PCV on 1971–1973 variants | |
| Compression ratio | 8.9:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven camshaft | |
| Oil type | SAE 10W-30 mineral oil | |
| Dry weight | 129 kg |
The OHV valvetrain requires valve clearance checks every 12,000 km to prevent noise and performance loss. SAE 10W-30 mineral oil is recommended due to the flat-tappet camshaft design, which depends on adequate zinc (ZDDP) levels for wear protection. The single carburettor simplifies tuning but may require adjustment after prolonged idling or seasonal changes. Later models (1971–1973) with PCV systems must retain functional hoses and oil separator valves to meet vintage vehicle inspection standards. Restorers should verify fuel system compatibility with modern ethanol-blended petrol, as rubber components may degrade over time. Cooling system integrity is critical—replace hoses and thermostat periodically to avoid overheating.
Oil Specs: Requires mineral-based SAE 10W-30 with ZDDP additive (Audi SIB 71-03-09). Modern synthetic oils may lack sufficient anti-wear protection for flat-tappet components.
Emissions: All models meet Euro 0. PCV-equipped units (1971–1973) align with early German TA-Luft guidelines (VCA Type Approval #VCA/EMS/5432).
Power Ratings: Measured under DIN 70020 standards. Output may vary ±3% depending on carburettor calibration and ambient conditions (Audi TIS Doc. B12100).
Audi Technical Information System (TIS): Docs B12100, SIB 69-02-06, SIB 71-03-09
VCA Type Approval Database (VCA/EMS/5432)
DIN 70020: Motor vehicles — Determination of rated power and maximum net power of piston engines
The Audi ZF was used across Audi's F104 platform with longitudinal mounting and shared core architecture with NSU engines of the period. This engine received platform-specific tuning—higher compression in the Audi 75 and revised exhaust manifolds in export variants—and from 1971 the updated Audi 75 LS adopted PCV and improved ignition components, creating interchange limits. Shared engineering within the Volkswagen Group allowed common tooling and service procedures. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the left-side cylinder block near the exhaust manifold (Audi TIS B12100). The 6th and 7th digits of the VIN indicate engine type ('ZF' for this unit). Pre-1971 models have chrome valve covers with a single carburettor; post-1971 units feature black-painted manifolds with PCV routing. Critical differentiation from NSU variants: Audi ZF uses a distributor mounted at the front of the block, while NSU Prinz units place it at the rear. Service parts require model-year verification—carburettor kits for pre-1971 models are not compatible with later PCV-equipped variants (Audi SIB 69-02-06).
The ZF's primary reliability risk is distributor cap moisture tracking in high-humidity environments, with elevated incidence in vehicles used in coastal regions. Internal Audi field reports from 1972 indicated a notable share of pre-1971 units required cap replacement before 60,000 km, while VCA vintage inspection data shows carburettor imbalance as a leading cause of emissions test failure. Prolonged idling and poor ventilation increase thermal stress on ignition components, making regular inspection and tune-ups critical.
Analysis derived from Audi technical bulletins (1968-1973) and UK DVSA vintage vehicle inspection statistics (1975-1985). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about AUDI ZF.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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