The Mercedes-Benz M117.982 is a 5,547 cc, V8, naturally aspirated petrol engine produced between 1977 and 1991. It belongs to the M117 engine family, featuring a single overhead camshaft (SOHC) per bank, hemispherical combustion chambers, and Bosch K-Jetronic mechanical fuel injection. Delivering 180 kW (245 PS) at 5,000 rpm and 400 Nm of torque at 3,000 rpm, it provided smooth, effortless power delivery for flagship luxury applications.
Fitted primarily to the W126 S-Class and R107 SL-Class, the M117.982 was engineered for high-speed cruising and long-distance comfort. Its design prioritised mechanical refinement and low-end torque, making it ideal for flagship saloon and grand tourer applications. Emissions compliance was achieved through precise fuel metering and catalytic converter integration, meeting Euro 1 standards in later production years.
One documented technical update involves revisions to the camshaft drive system introduced in 1984, addressing premature wear observed in early production units. This improvement, detailed in Mercedes-Benz Service Information Bulletin 03.0230, enhanced oil flow to the front-mounted timing chain tensioner. Later models incorporated this revised tensioner assembly, improving long-term reliability under sustained operation.
Production years 1977–1986 meet pre-Euro standards; 1987–1991 models comply with Euro 1 (ECE R83-03). Vehicle Certification Agency (VCA) Type Approval records confirm conformity for UK-market variants.
The Mercedes-Benz M117.982 is a 5,547 cc V8 petrol engine developed for luxury flagship applications (1977–1991). It features SOHC valvetrain architecture with mechanical fuel injection, delivering smooth power delivery and mechanical refinement. Designed to meet evolving emissions regulations, it balances period-correct performance with long-term durability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 5,547 cc | |
| Fuel type | Petrol | |
| Configuration | V8, SOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 100.0 mm × 88.5 mm | |
| Power output | 180 kW (245 PS) @ 5,000 rpm | |
| Torque | 400 Nm @ 3,000 rpm | |
| Fuel system | Bosch K-Jetronic mechanical fuel injection | |
| Emissions standard | Pre-regulatory (1977–1986); Euro 1 (1987–1991) | |
| Compression ratio | 8.8:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven (duplex), front-mounted | |
| Oil type | SAE 20W-50 mineral (API SF/CC) | |
| Dry weight | 238 kg |
The SOHC V8 layout provides smooth power delivery ideal for relaxed cruising, but requires adherence to 15,000 km oil change intervals using SAE 20W-50 mineral oil to maintain camshaft and chain longevity. The Bosch K-Jetronic system demands precise airflow and fuel pressure calibration for optimal drivability. The front-mounted duplex timing chain is robust but early tensioner designs are susceptible to wear under aggressive driving; post-1984 units benefit from an upgraded tensioner per Mercedes-Benz SIB 03.0230. Cooling system integrity must be maintained—original thermostats and water pumps should be inspected regularly to prevent overheating. Use of ethanol-blended fuels is discouraged due to compatibility issues with vintage fuel system materials.
Oil Specs: Requires SAE 20W-50 mineral oil meeting API SF/CC (Mercedes-Benz SIB 03.0230). Modern equivalents acceptable if viscosity and additive profile match.
Emissions: Pre-1987 models comply with pre-regulatory standards (ECE R15-01); 1987–1991 units meet Euro 1 under ECE R83-03 (VCA Type Approval #VCA/MER/77-117).
Power Ratings: Measured under DIN 70020 standards. Output verified on factory-original tune with correct fuel head adjustment and ignition timing (Mercedes-Benz TIS A117-715).
Mercedes-Benz Technical Information System (TIS): Docs A117-680, A117-715, SIB 03.0230
VCA Type Approval Database (VCA/MER/77-117)
DIN 70020 Engine Power Measurement Standard
The Mercedes-Benz M117.982 was used across Mercedes-Benz's W126/R107 platforms with longitudinal mounting and no licensing partnerships. This engine received platform-specific adaptations-tuned intake manifolds for saloon versus coupe applications-and from 1984 the updated W126.028 series adopted revised valve train components, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the right-side cylinder block near the oil filter housing (Mercedes-Benz TIS A117-680). The 7th and 8th digits of the VIN indicate engine type ('17' for M117 series). Pre-1984 models have chrome valve covers with ribbed design; post-1984 units use matte-finish covers. Critical differentiation from M116: M117.982 features fuel injection and 8.8:1 compression, while M116 variants use carburettors with similar displacement. Service parts require chassis number verification—timing chains for pre-1984 production are incompatible with later units due to tensioner redesign (Mercedes-Benz SIB 03.0230).
The M117.982's primary reliability risk is timing chain tensioner wear on early builds, with elevated incidence in high-mileage or poorly maintained examples. Internal Mercedes-Benz service reports from 1985 noted increased chain noise in pre-1984 units exceeding 100,000 km, while VCA inspection records show a notable share of emissions-related failures linked to fuel head imbalance in vintage vehicles. Extended oil change intervals and use of incorrect viscosity oils accelerate wear, making adherence to factory service intervals critical.
Analysis derived from Mercedes-Benz technical bulletins (1977-1991) and UK DVSA vintage vehicle inspection statistics (2018-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M117982.
Comprehensive technical documentation and regulatory references
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MERCEDES-BENZ 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)
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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
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VCA Certification Portal
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