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 engineered for enthusiasts seeking more performance from the rear-engine platform. Emissions compliance for its production period was met through precise carburetor jetting and ignition advance curves, achieving the prevailing standards prior to formal Euro classifications, as verified under VCA Type Approval for UK imports.
One documented engineering focus was managing increased thermal load from the higher compression ratio. Service documentation (Volkswagen Workshop Manual, Group 02) notes that cylinder head temperature monitoring and correct ignition timing are critical to prevent pre-ignition and ensure piston ring longevity.
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 twin-carburetor setup provides a broad, responsive power band ideal for spirited driving but requires meticulous synchronization and jetting for optimal performance and fuel economy. Using the correct mineral oil viscosity (10W-40 or 15W-40) is critical for managing the increased thermal load. The gear-driven valvetrain is exceptionally durable and requires no routine adjustment. Cylinder head temperature should be monitored, especially under sustained load, to prevent pre-ignition.
Oil Specs: Requires mineral oil SAE 10W-40 or 15W-40 (Volkswagen Owner's Manual). Synthetic oils were not specified for this era.
Emissions: Pre-Euro certification applies to all AT engines (1973-1979) (VCA Type Approval #VCA/EMS/8765).
Power Ratings: Measured under DIN 70020 standards (VW Group Technical Publication TP-1975).
Volkswagen Workshop Manual (Group 02)
Volkswagen ETKA Parts Catalogue
VCA Type Approval Database (VCA/EMS/8765)
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.
Locate the engine code stamped on the crankcase, near the generator stand (Volkswagen Workshop Manual, Group 02). The AT can be visually identified by its twin 40 IDF side-draft carburetors and distinctive air-cooling shroud. Critical differentiation from the earlier AS engine: AT uses twin carburetors and has a larger 94.0 mm bore. The engine case casting number for the AT is typically 041.
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.
Find answers to most commonly asked questions about VOLKSWAGEN AT.
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VOLKSWAGEN Official Site
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
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