MG Car Engine – Magnette Mk 4, Maestro, Montego

Published by Carl Wilson on

MG got its name from “Morris Garages” and carried a variety of engines. The MG Midget MkI (1961-1964). This was the first version, essentially a badge engineered version of the Austin-Healey Sprite MKII and retained the quarter elliptic sprung rear axle from the original Sprite. The engine was a 948 cc A-Series with twin SU carburettors producing 46 hp (34 kW) at 5500 rpm and 53 ft·lbf (72 Nm) at 3000 rpm. Reconditioned, Used or Secondhand MG car engines are availble here.

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The MG Midget MkII (1964-1966). The engine got better (1098 cc A-Series I4) bearings allowing the power to be increased to 59 hp (44 kW) at 5750 rpm and torque to 65 lbf·ft (88 Nm) at 3500 rpm.

The MG Midget MkIII (1966-1974). The engine now grew to 1275 cc A-Series I4 using the development seen on the Mini Cooper S. Output was 65 hp (48 kW) at 6000 rpm and 72 ft·lbf (98 Nm) at 3000 rpm. However, this was a de-tuned version of the engine that was given to the Cooper S. The Midget retained the standard 12G940 cylinder head casting that was common to other BMC 1300 cars, whereas the Cooper S had a special head with an extra two bolts to fasten it to the cylinder block.
The MG Midget 1500 (1974-1979). The A-Series engine was dropped to be replaced by the 1493 cc unit from the Triumph Spitfire.

The meaning of A-Series I4.

  • BMC A-Series engine is a small straight-4 automobile engine, the A-Series, is one of the most common in the world. The straight-4 or inline-4 is an internal combustion engine with four cylinders aligned in one row. Nicknamed a four-banger, this straight engine configuration is the most common in cars with a displacement up to 2.3 litres. The current “practical” limit to the displacement of straight-4 engines in a car is around 2.7 litres. However, in tractors and other construction machinery, four-cylinder diesel engines with a displacement of 4.5 litres and above can still be found.
  • The straight-4 (I4) engine is not a balanced configuration. While a pair of pistons is always moving up at the same time as the other pair is moving down, piston speed – as with all internal combustion engines – is higher through the top 180 degrees of the stroke than the bottom 180 degrees, which leads to a secondary harmonic imbalance. While this is tolerable in a small low-displacement low-power configuration, the vibrations get worse with increasing size and power. Most straight-4 engines below 2.0 L in displacement rely on the damping effect of their engine mounts. Today, most engineers will make use of balance shafts above that limit. A 4-cylinder engine needs two balance shafts, rotating at twice the crankshaft frequency, to be smooth. Nevertheless, there were several samples of larger straight-4s in production using no balance shafts, such as the Citroën DS 23 2347 cc engine that was a derivative of the Traction Avant engine, and the 1948 Austin 2660 cc engine used in the Austin-Healey 100 and Austin Atlantic. These engines were generally the result of a long incremental evolution process and their power was kept relatively low regarding their capacity.

The roadster was the first of the MGB range to be produced. It had a BMC B-Series I4 engine. BMC B-Series was a straight-4 automobile engine family created as a larger alternative to the company’s A-Series. Displacements ranged from 1.2 L, 1.6 L, and even 2.4 L. Available production was the MKII, MKIII, MGB GT, MGC this was a 2911 cc, straight-6 version, MG began offering the MGB GT V8MG RV8 was a V8 3946 cc.

The meaning of B-Series.

  • The BMC B-Series engine was of conventional construction with a one piece crankcase and cylinder block in cast iron with cylinder head also usually in cast iron. The sump was made from pressed steel. Early engines used a three bearing crankshaft but later engines used five bearings. On all except the rare twin overhead camshaft variant the camshaft, which was chain driven and mounted low in the block, operated the overhead valves via pushrods and rocker arms. The two inlet ports in the non-crossflow cylinder head were shared between cylinders 1 + 2 and 3 + 4 and the three exhaust ports between cylinder 1, 2 + 3 and 4. Valve clearance was adjustable by screws on the rocker arms with access to the tappets by two side covers on the engine block, this feature being a probable hang over from side valve engine design.

Other recent models included:
1961-1968 MG Magnette Mk. IV
1983-1991 MG Maestro
1985-1991 MG Montego
1985 MG E-XE
1995-2005 MG F
2002-2005 MG TF
2001-2005 MG ZR
2001-2005 MG ZS
2001-2005 MG ZT
2002-2005 MG XPower SV
1980s MG Metro van
2003-2005 MG Express

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Categories: ArticlesMG

Carl Wilson

You won't believe it, I'm native Scotsman. Enthusiast. Car lovers. Almost finished rebuilding my Reliant Saber 🔥

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