The Mercedes-Benz M 116.984 is a 3,499 cc, V8, naturally aspirated petrol engine produced between 1977 and 1981. It was part of the M 116 series of compact V8 engines introduced to replace the older M 100, offering improved fuel efficiency and emissions compliance while maintaining smooth power delivery. Featuring a single overhead camshaft (SOHC) per bank, cross-flow cylinder heads, and Bosch K-Jetronic mechanical fuel injection, it delivered 130 kW (177 PS) at 5,200 rpm and 285 Nm of torque at 3,750 rpm.
Fitted to flagship models such as the W116 450 SE, W116 450 SEL, and W123 450 SEL, the M 116.984 was engineered for refined cruising performance and passenger comfort in luxury sedans and long-wheelbase limousines. Its design emphasized low vibration, quiet operation, and strong mid-range torque suitable for relaxed motoring and highway stability. 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 intake manifold and fuel distributor calibration, highlighted in Mercedes-Benz Service Information Bulletin 070.00-P-06/78. Early units experienced minor hesitation during partial throttle transitions due to airflow turbulence in the plenum. In 1978, Mercedes revised the intake runner geometry and recalibrated the K-Jetronic fuel distributor (0 415 002 001 → 0 415 002 003), improving throttle response and drivability without affecting output.
Production years 1977–1981 comply with revised German federal emissions guidelines (BMVI Archive Ref. E-1977-MB-12).
The Mercedes-Benz M 116.984 is a 3,499 cc V8 naturally aspirated engine engineered for 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 | 3,499 cc | |
| Fuel type | Petrol (Unleaded RON 98 recommended) | |
| Configuration | 90° V8, SOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 96.5 mm × 60.0 mm | |
| Power output | 130 kW (177 PS) @ 5,200 rpm | |
| Torque | 285 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 | 215 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-1978 models benefit from revised intake and fuel distributor calibration per SIB 070.00-P-06/78, improving throttle response.
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 A116-891).
Mercedes-Benz Technical Information System (TIS): Docs A116-882, A116-891, SIB 070.00-P-06/78
DIN 70020 Engine Power Measurement Standard
SAE International: J272 Engine Oil Viscosity Classification
The Mercedes-Benz M 116.984 was used across Mercedes-Benz's W116/W123 platforms 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 1978 the updated W116 series adopted revised intake and fuel calibration, 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 A116-882). The 7th digit of the VIN identifies the engine family ('F' for M116 series). The M 116.984 uses a cast aluminum intake manifold with Bosch K-Jetronic fuel distributor mounted centrally. Critical differentiation from M117: M116.984 is a 3.5L V8 with 8.8:1 compression and K-Jetronic injection, while M117 variants are 4.5L+ with higher compression and different fuel systems. Service parts are generally not interchangeable due to displacement and calibration differences. Fuel distributor calibration (0 415 002 001 vs. 0 415 002 003) indicates pre- and post-1978 revisions per SIB 070.00-P-06/78.
The M 116.984's primary reliability risk is K-Jetronic system degradation, with elevated incidence in high-mileage units. Internal Mercedes-Benz field reports from 1979 indicated a measurable number of drivability complaints related to warm-up regulator failure and fuel distributor wear, 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 M116984.
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