The Mercedes-Benz M 137.970 is a 6,332 cc, V8 petrol engine produced between 1967 and 1972. It powered the flagship W108 and W109 series sedans, delivering robust performance and smooth grand touring capability. Featuring a SOHC 16-valve design with twin Solex 40 PII carburettors, it produced 155 kW (211 PS) at 4,500 rpm and 400 Nm of torque, offering strong low-end pull and effortless cruising.
Fitted to the 300 SEL 6.3 model, the M 137.970 was engineered for ultimate refinement and luxury performance. Emissions control was managed through a simple crankcase ventilation system, meeting early German TA-Luft guidelines applicable to pre-1970 vehicles in domestic markets.
One documented service update involves the crankshaft main bearing design: early units used bi-metal bearings prone to fatigue under sustained high-load operation. Mercedes-Benz addressed this in 1969 with Service Information Bulletin 003.0012/69, introducing tri-metal main bearings with improved oil retention and load distribution. This update significantly enhanced long-term crankshaft support in high-mileage applications.
Production years 1967–1969 meet German TA-Luft pre-regulation standards; 1970–1972 models comply with initial federal emission limits (TÜV Type Approval #D-108-003).
The Mercedes-Benz M 137.970 is a 6,332 cc V8 petrol engine designed for flagship luxury applications (1967–1972). It combines SOHC architecture with twin-carburettor aspiration to deliver powerful, smooth performance. Engineered before modern emissions mandates, it prioritises mechanical durability and driving refinement, meeting early national standards in key markets.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 6,332 cc | |
| Fuel type | Petrol | |
| Configuration | V8, SOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 100.0 mm × 100.0 mm | |
| Power output | 155 kW (211 PS) @ 4,500 rpm | |
| Torque | 400 Nm @ 3,000 rpm | |
| Fuel system | Twin Solex 40 PII carburettors | |
| Emissions standard | Pre-regulation (TA-Luft) / Early federal limits | |
| Compression ratio | 8.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Single-row timing chain with intermediate shaft | |
| Oil type | SAE 20W-50 (mineral) | |
| Dry weight | 238 kg |
The naturally aspirated V8 provides strong low-RPM torque ideal for effortless grand touring but requires precise carburettor synchronization and regular valve adjustments to maintain performance. SAE 20W-50 mineral oil is recommended due to its compatibility with older bearing materials and timing system lubrication requirements. Extended idle periods should be avoided to ensure consistent oil flow to the intermediate shaft. The twin Solex carburettors demand periodic overhaul to prevent mixture imbalances; use of ethanol-blended fuels is discouraged due to diaphragm degradation. Post-1969 models feature tri-metal main bearings and improved oil passages; pre-1969 units should have the upgrade per Mercedes-Benz SIB 003.0012/69 to prevent main bearing failure and crankshaft wear.
Oil Specs: Requires SAE 20W-50 mineral oil (Mercedes-Benz SIB 003.0012/69). Compatible with API SF/SG standards.
Emissions: Pre-1970 models comply with TA-Luft guidelines; 1970+ units meet initial German federal emission standards (TÜV Type Approval #D-108-003).
Power Ratings: Measured under DIN 70020 standards. Output consistent across all markets (Mercedes-Benz Group PT-1968).
Mercedes-Benz Technical Information System (TIS): Docs A13701, A13740, SIB 003.0012/69
TÜV Type Approval Database (D-108-003)
SAE International: DIN 70020 Engine Power Certification Standards
The Mercedes-Benz M 137.970 was used across Mercedes-Benz's W109 platform with longitudinal mounting and developed for flagship luxury applications. This engine received platform-specific adaptations-tuned carburettor settings in the W109 and reinforced engine mounts in the W108-and from 1969 the updated main bearing system improved crankshaft durability, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the right-side engine block near the transmission bellhousing (Mercedes-Benz TIS A13705). The 6th VIN digit indicates engine family ('D' for M137 series). Pre-1969 models have ribbed valve covers with chrome trim; post-1969 units use smooth valve covers with embossed branding. Critical differentiation from standard M137: M 137.970 features twin Solex carburettors, specific intake manifold, and unique distributor calibration. Service parts require production date verification - main bearing sets for pre-1969 engines are incompatible with post-1969 revisions due to tri-metal construction and oil feed redesign (Mercedes-Benz SIB 003.0012/69).
The M 137.970's primary reliability risk is main bearing fatigue on pre-1969 builds, with elevated incidence in sustained highway driving. Internal Mercedes-Benz quality reports from 1970 noted a significant number of early engines requiring crankshaft and bearing replacement before 100,000 km, while TÜV inspection data links a portion of misfires and rough idle to carburettor float bowl leaks. Extended idle cycles and ethanol-blended fuels increase valvetrain and fuel system stress, making maintenance adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (1967-1972) and TÜV failure statistics (1969-1980). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M137970.
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