The Mercedes-Benz M114.980 is a 2,496 cc, inline-six, naturally aspirated petrol engine produced between 1965 and 1971. It formed part of the M114 engine family, featuring a single overhead camshaft (SOHC), hemispherical combustion chambers, and twin Zenith 36/40 INAT carburettors. Delivering 115 kW (156 PS) at 5,500 rpm and 211 Nm of torque at 4,000 rpm, it offered refined performance for its era.
Fitted primarily to the W114 250 and W115 250 models, the M114.980 was engineered for smooth cruising and long-distance comfort. Its design prioritised mechanical refinement and durability over outright power, making it suitable for executive saloon applications. Emissions were managed through basic crankcase ventilation and precise carburettor tuning, meeting pre-regulatory European standards of the time.
One documented service update involves the replacement of early camshaft drive chain tensioners, which were prone to wear under sustained high-load operation. This issue, referenced in Mercedes-Benz Service Information Bulletin 03.0182, stemmed from insufficient oil pressure supply to the tensioner mechanism. Later production units incorporated an improved tensioner design to enhance long-term reliability.
Production years 1965–1971 comply with pre-Euro emissions standards as defined under ECE Regulation 15 (Revision 01). Vehicle Certification Agency (VCA) Type Approval records confirm conformity for UK-market variants.
The Mercedes-Benz M114.980 is a 2,496 cc inline-six petrol engine engineered for executive saloon applications (1965–1971). It combines SOHC valvetrain architecture with twin carburettor induction to deliver linear power delivery and mechanical refinement. Designed prior to modern emissions regulations, it balances period-correct performance with long-term durability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,496 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-6, SOHC, 12-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.0 mm × 70.0 mm | |
| Power output | 115 kW (156 PS) @ 5,500 rpm | |
| Torque | 211 Nm @ 4,000 rpm | |
| Fuel system | Twin Zenith 36/40 INAT carburettors | |
| Emissions standard | Pre-regulatory (ECE R15-01) | |
| Compression ratio | 9.0:1 | |
| 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 | 185 kg |
The SOHC inline-six 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. Correct carburettor synchronization is essential for idle stability and fuel efficiency. The front-mounted duplex timing chain is robust but early tensioner designs are susceptible to wear under aggressive driving; post-1968 units benefit from an upgraded tensioner per Mercedes-Benz SIB 03.0182. 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 03.0182). Modern equivalents acceptable if viscosity and additive profile match.
Emissions: Pre-regulatory compliance under ECE Regulation 15 (Revision 01) applies to all production years (VCA Type Approval #VCA/MER/65-114). No Euro standards existed during production period.
Power Ratings: Measured under DIN 70020 standards. Output verified on factory-original tune with correct carburettor jetting and ignition timing (Mercedes-Benz TIS A114-715).
Mercedes-Benz Technical Information System (TIS): Docs A114-680, A114-715, SIB 03.0182
VCA Type Approval Database (VCA/MER/65-114)
DIN 70020 Engine Power Measurement Standard
The Mercedes-Benz M114.980 was used across Mercedes-Benz's W114/W115 platforms with longitudinal mounting and no licensing partnerships. This engine received platform-specific adaptations-tuned intake manifolds for saloon versus coupe applications-and from 1968 the updated W114.020 series adopted revised valve train components, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the left-side cylinder block near the bellhousing flange (Mercedes-Benz TIS A114-680). The 7th and 8th digits of the VIN indicate engine type ('14' for M114 series). Pre-1968 models have chrome valve covers with ribbed design; post-1968 units use matte-finish covers. Critical differentiation from M115: M114.980 features twin carburettors and 9.0:1 compression, while M115 variants are fuel-injected with higher compression. Service parts require chassis number verification—timing chains for pre-1968 production are incompatible with later units due to tensioner redesign (Mercedes-Benz SIB 03.0182).
The M114.980'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 1969 noted increased chain noise in pre-1968 units exceeding 100,000 km, while VCA inspection records show a notable share of emissions-related failures linked to carburettor 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 (1965-1971) 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 M114980.
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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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