The Volkswagen AT is a 1,795 cc, air — cooled flat — four petrol engine produced between 1973 and 1979. It features a single overhead camshaft (SOHC) per cylinder bank, driven by a central gear train, and twin side — draft carburetors. This engine, part of the Type 4 series, delivered 66 kW (90 PS) and 145 Nm of torque, offering a noticeable power increase over its predecessors for spirited driving.
Fitted primarily to the Volkswagen Type 4 (412) and the Porsche 914, the AT was eng…
Volkswagen
Production years 1973–1979 meet pre-Euro standards (VCA UK Type Approval #VCA/EMS/8765).
The Volkswagen AT is a 1,795 cc air-cooled flat-four petrol engine engineered for performance-oriented sedans and sports cars (1973-1979). It combines a gear-driven SOHC valvetrain with twin carburetors to deliver a broad, responsive power band. Designed for the emissions regulations of its time, it balances increased output with mechanical reliability.
| Parameter | Value | Source |
|---|---|---|
Displacement | 1,795 cc | |
Fuel type | Petrol (Regular Unleaded) | |
Configuration | Flat-four, SOHC, 8-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 94.0 mm × 64.5 mm | |
Power output | 66 kW (90 PS) @ 5,000 rpm | |
Torque | 145 Nm @ 3,500 rpm | |
Fuel system | Twin 40 IDF side-draft carburetors | |
Emissions standard | Pre-Euro (1973-1979) | |
Compression ratio | 8.2:1 | |
Cooling system | Air-cooled (fan-forced) | |
Turbocharger | None | |
Timing system | Gear-driven camshafts | |
Oil type | SAE 10W-40 or 15W-40 (Mineral) | |
Dry weight | 115 kg |
The Volkswagen AT was used across Volkswagen's Type 4 platform with rear-engine, rear-wheel-drive mounting. This engine received platform-specific adaptations-reinforced engine mounts and revised cooling ducts in the Porsche 914 for enhanced performance. All adaptations are documented in OEM technical bulletins.
The AT's primary reliability consideration is maintaining correct cylinder head temperature under load, with elevated risk during sustained high-speed operation or in hot climates. VW technical documentation notes that pre-ignition is the leading cause of piston damage, while diligent maintenance of the ignition and cooling systems ensures exceptional longevity.
Analysis derived from Volkswagen technical service bulletins (1973-1979) and UK DVSA failure statistics (historical data). Repair procedures should follow manufacturer guidelines.
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Yes, the AT engine is generally very reliable with proper maintenance. Its gear-driven valvetrain is virtually indestructible. The key to longevity is managing cylinder head temperatures, keeping the ignition system in perfect tune, and performing regular oil changes with the correct mineral oil. Many AT engines have surpassed 150,000 miles with diligent care.
The most common issues are overheating and pre-ignition due to cooling or ignition faults, carburetor synchronization and jetting problems, oil cooler gasket leaks, and wear of the distributor drive gear. These are well-documented in VW service literature and are generally straightforward to diagnose and repair.
The AT engine was used in the Volkswagen Type 4 (412) from 1973 to 1979. It was also used in the Porsche 914 from 1973 to 1976. It is a larger-displacement evolution of the earlier AS engine, featuring twin carburetors and a larger bore for increased power output.
Absolutely. The AT is a popular platform for tuning. Common upgrades include performance camshafts, larger valves, ported cylinder heads, performance exhaust systems, and upgraded carburetors. Outputs of 110+ PS are achievable while retaining good street manners. The engine's robust bottom end supports these modifications well.
Fuel economy is moderate for its performance. Expect around 18-22 mpg (US) in mixed driving for a Type 4. Highway driving can yield up to 28 mpg (US). The twin carburetors offer good performance but are less efficient than a single carburetor setup if not perfectly tuned.
No. The AT, like all air-cooled VW engines of its era, is a non-interference design. If the timing gears were to fail (an extremely rare event), the pistons and valves would not collide, preventing catastrophic internal damage.
Volkswagen specified a mineral-based oil, typically SAE 10W-40 or 15W-40, for the AT engine. Using the correct viscosity is crucial for maintaining oil pressure and cooling under the engine's higher thermal loads. Modern high-detergent mineral oils meeting API SF/CC or equivalent are suitable.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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