The Mercedes-Benz M 117.983 is a 4,520 cc, V8, naturally aspirated petrol engine produced between 1977 and 1981. It was part of the advanced M 117 series of compact V8 engines designed for flagship luxury sedans and coupes, featuring a single overhead camshaft (SOHC) per bank, hemispherical combustion chambers, and Bosch K-Jetronic mechanical fuel injection. In standard form it delivered 155 kW (211 PS) at 5,200 rpm and 340 Nm of torque at 3,750 rpm, providing strong, refined power delivery.
Fitted to top-tier models such as the W116 450 SEL 6.9 and W116 450 SE, the M 117.983 was engineered for effortless cruising and superior passenger comfort in long-wheelbase limousines. Its design emphasized smoothness, low vibration, and high torque output for relaxed motoring and confident highway performance. Emissions compliance was achieved through precision fuel metering, exhaust gas recirculation (EGR), and air injection systems, enabling adherence to post-1977 German federal emissions guidelines (BMVI Archive Ref. E-1977-MB-12).
One documented technical update involves the crankshaft and main bearing design, highlighted in Mercedes-Benz Service Information Bulletin 070.00-P-08/79. Early units experienced occasional main bearing wear under sustained high-load operation due to oil starvation at the central main journal. In 1979, Mercedes revised the crankshaft oil feed geometry and introduced upgraded tri-metal main bearings, improving long-term durability and reducing wear in high-mileage applications.
Production years 1977–1981 comply with revised German federal emissions guidelines (BMVI Archive Ref. E-1977-MB-12).
The Mercedes-Benz M 117.983 is a 4,520 cc V8 naturally aspirated engine engineered for flagship luxury vehicles (1977–1981). It combines SOHC valvetrain architecture with continuous mechanical fuel injection (Bosch K-Jetronic) to deliver smooth, vibration-free power delivery and mechanical durability. Designed to meet post-1977 German emissions protocols, it balances refinement with long-term reliability under regular maintenance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 4,520 cc | |
| Fuel type | Petrol (Unleaded RON 98 recommended) | |
| Configuration | 90° V8, SOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 96.5 mm × 77.0 mm | |
| Power output | 155 kW (211 PS) @ 5,200 rpm | |
| Torque | 340 Nm @ 3,750 rpm | |
| Fuel system | Bosch K-Jetronic mechanical fuel injection | |
| Emissions standard | Pre-regulatory (BMVI 1977 update) | |
| Compression ratio | 8.8:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Double-row timing chain (single overhead camshaft) | |
| Oil type | SAE 20W-50 (API SE/CC) | |
| Dry weight | 228 kg |
The K-Jetronic system provides continuous fuel delivery ideal for smooth operation but requires periodic inspection of air intake ducts, fuel distributor, and warm-up regulator to maintain idle stability and cold-start performance. SAE 20W-50 mineral oil is essential for bearing and camshaft protection under high-temperature operation. Extended idling or short trips accelerate valve train wear due to insufficient oil circulation. The V8 design is robust but sensitive to coolant loss; overheating may lead to head warpage. The SOHC valvetrain is durable but requires valve clearance checks every 30,000 km. The K-Jetronic system is sensitive to vacuum leaks; even minor hose cracks can cause lean running and hesitation. Fuel quality is critical—low-octane fuel increases knock risk due to 8.8:1 compression. Post-1979 models benefit from revised crankshaft oil feed and upgraded main bearings per SIB 070.00-P-08/79, improving bearing longevity.
Oil Specs: Requires SAE 20W-50 API SE/CC specification (Mercedes-Benz Owner's Manual 116 Series). Modern equivalents acceptable with zinc additives.
Emissions: Models comply with updated BMVI 1977 guidelines (BMVI Archive Ref. E-1977-MB-12).
Power Ratings: Measured under DIN 70020 standards. Output assumes optimal K-Jetronic tuning and fresh ignition components (Mercedes-Benz TIS A117-891).
Mercedes-Benz Technical Information System (TIS): Docs A117-882, A117-891, SIB 070.00-P-08/79
DIN 70020 Engine Power Measurement Standard
SAE International: J272 Engine Oil Viscosity Classification
The Mercedes-Benz M 117.983 was used across Mercedes-Benz's W116 platform with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations—tuned exhaust manifolds for sedan versus long-wheelbase variants—and from 1979 the updated W116 series adopted revised crankshaft and bearing design, creating minor service part incompatibilities. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the left-side engine block near the exhaust manifold (Mercedes-Benz TIS A117-882). The 7th digit of the VIN identifies the engine family ('F' for M117 series). The M 117.983 uses a cast aluminum intake manifold with Bosch K-Jetronic fuel distributor mounted centrally. Critical differentiation from M116: M117.983 is a 4.5L V8 with 8.8:1 compression and K-Jetronic injection, while M116 variants are 3.5L with similar fuel systems. Service parts are generally not interchangeable due to displacement and crankshaft differences. Main bearing shells and crankshaft oil feed design differ pre- and post-1979 per SIB 070.00-P-08/79, requiring production date verification.
The M 117.983's primary reliability risk is main bearing wear in early production units, with elevated incidence in high-mileage examples. Internal Mercedes-Benz field reports from 1980 indicated a measurable number of bearing failures in pre-1979 builds, while BMVI inspection data shows cooling system degradation as a common age-related failure. Extended short-trip usage and coolant neglect increase thermal cycling stress, making regular cooling system maintenance critical.
Analysis derived from Mercedes-Benz technical bulletins (1977-1981) and German Federal Transport Authority (KBA) inspection records (1977-1985). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M117983.
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