Mercedes-Benz M130 engine
The Mercedes Benz M130 Engine was the last and largest of the ‘mid-sized’ Single Over Head Camshaft (SOHC) straight-6 cylinder (inline) engines produced by Mercedes Benz. The ‘mid-sized six’ started life as the 2.2 litre M180 (2,197cc/133ci) which was unveiled at the Frankfurt Motor show in September 1951 alongside the new 3.0 litre M186 ‘big’ straight-6. These engines were used to power the 220 and 300 models of the 1951 Mercedes range. While sharing many design features such as staggered valve arrangement and rockers running off a single overhead camshaft driven by a duplex cam-chain, the engines were of completely different design with little or no inter-changeability of parts.1
The 'Big Six'
The 3.0 litre ‘big six’ was produced from 1951 until 1967 with no change in its 2,996 cc displacement derived from a slightly under-square 85 mm x 88mm bore and stroke. The various versions of the engine (M186 – M199) produced from 113 – 212 bhp (158 kW) as compression ratios rose and the number of carburettors multiplied or were replaced with fuel-injection. These engines powered the 300 Adenauer, 300S/Sc, 300SL, 300SE Fintail/Coupe/Cabrio (W111/112), 300SE/SEL (W108/109).2
M180 to M130
The ‘mid-sized’ six saw longer service, with production ceasing after some 20 years in 1971. Its last home was the W108 280SE in M130E (130.980) fuel-injected guise, and in M130V carburetted form, in the lower-powered 280S and the smaller W114 250/8 (2.8). The W108 itself lived on for another year, powered by 3.5 and 4.5 litre V8 (M116/M117) engines. However the replacement 280SE model W116 used the new double-overhead camshaft (DOHC) M110 2.8 litre engine, with the W114 "Compact' initially using the older configuration carburetted OHC M114 2.5 litre engines.
The first M180 engine (180.920) displaced 2,195 cc (133ci) and was rated at 80 hp (60 kW). It powered the W187 220 Sedan, Coupe and Cabriolet (Type A and B) from 1951 to 1955, and the W105 219 from 1956 to 1959; the later M180.920 giving around 100 hp (75 kW) for 220S. The W180 Ponton 6-cyinder 220 Sedans, Coupes and Cabriolets of 1955-1959 benefitted from the up-rated M180.924 which delivered 124 hp (92 kW). In 1958 Bosch mechanical fuel injection was added to the 2.2 litre six and the engine, now giving 113-134 hp, was redesignated M127. The M127 was fitted to the last of the Pontons: he rare 1958 W128 220SE, of which fewer than 4000 were produced. The M127 also powered the first series (1959-1965) of W111 ‘Fintail’ 220SE and 220SEb models, with the carburetted M180 in the 220b and 220Sb. The addition of the lower case ‘b’ was added to differentiate the Fintails from the earlier Pontons.
From 1965 the ‘New Generation’ or /8 models were introduced, with the W111/W112 sedans superseded by the new W108/109 chassis - apart from the W111 220b/Sb/SEb sedan which was continued up-rated to the 230S, produced up to 1968. All models in 1965 were given up-rated engines, the M180's bore being increased 2 mm to give 2306 cc for the 230 and 230S. The two-door W111 coupes and cabriolets were continued right though to 1971. The higher specification W112 300SE coupe and cabrios were discontinued in 1967, as was the 3-litre ‘big six’ engine. The gap left in the model lineup by the departure of the 300SE two-door models was filled by the W111 280SE coupe and cabriolet powered by the new 3.5 litre V8.
The new Mercedes-Benz W108 250S and 250SE gained new 2.5 litre (2,496cc) variants of the ‘mid size six’ - the carburetted M108 and fuel-injected M129 - as did the W111 250SE two-door models. The extra capacity was obtained by lengthening the stroke by 6 mm to 78.8 mm. The M129 was fitted with a mechanically controlled six-piston fuel injection pump. The new long-wheelbase W109 300 SE sedan was initially powered by big M189 fuel-injected 3.0 litre six until its discontinuation; it was then fitted with an enlarged version of the M129: the M130.
The M130 was the ultimate variant of the ‘mid sized six’ with a capacity of 2,778 cc, obtained by increasing the 2.5-litre versions' bore by 4 mm to 86.5 mm, the stroke remaining at 78.8 mm. This was the maximum practical enlargement of the engine given the limitations of the block as evidenced by the deletion of water passages between the cylinders.
1 Six Appeal, Mercedes Enthusiast, May 2007, pp 52-58