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    Moderator Editor_Reid's Avatar
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    What is (and isn't) an Austin-Healey 100M?

    There is a continuing significant degree of confusion about the subject of what constitutes a 100M. Therefore I'd like to offer an article that I researched and wrote in 2005, the 50th anniversary of the introduction of the 100M.


    Reid Trummel

    For many years this question has been discussed and argued, misunderstood and sometimes even misrepresented, and it has frequently been a source of much confusion. However, a careful review of Healey history provides the simple answer:

    In the fall of 1955, at the Earls Court Motor Show in London, a new Austin-Healey model named the 100M was introduced. The Austin Motor Company production records indicate that 640 examples of this model were made between September 5, 1955 and July 16, 1956. All 640 were from the BN2 series, and it is these 640 cars, and these 640 cars only, that were named and marketed as the 100M. They are the only cars that are properly called “100M.”

    Unfortunately, the model name 100M is often loosely applied to a wide range of Austin-Healeys, series BN1 and BN2, which are fitted with certain aftermarket accessories and equipment. However, these cars are not 100M models, and a brief review of history demonstrates how and why this confusion has arisen.

    In early 1953, while Austin was still preparing to commence regular series production of the new Austin-Healey 100 at its factory in Longbridge, the Donald Healey Motor Company in Warwick ("the works") prepared four early pre-production cars (essentially hand-built prototypes of the Austin-Healey 100, series BN1) for the 24-hour race at Le Mans, France, that year. These were lightly modified standard cars. Two were entered in the race and achieved great success by finishing 12th and 14th overall in a field that included many highly modified and purpose-built race cars.

    Soon after that race, owners of standard cars began to inquire about performance upgrades, and the works undertook to offer the parts that had been used on those otherwise standard cars that raced at Le Mans, plus some other aftermarket accessories and racing equipment. These parts were listed in a booklet published as Austin Publication No. 1131, titled "Austin-Healey Hundred (Model B.N.1.) Special Equipment and Tuning Instructions."

    Among the many items listed in this booklet, probably the best-known was the “Le Mans Engine Modification Kit” (or simply “Le Mans Kit”), and it was sold as Part No. P.280, beginning in late 1953 or perhaps early in 1954. Some of these kits were fitted to cars by owners and some were fitted by dealers, and some were even fitted at the Donald Healey Motor Company for those owners able to take their cars there for the installation. The principal elements of the Le Mans Kit were:

    • Twin 1 3/4-inch H6 SU carburetors.
    • Aluminum intake manifolds.
    • Carburetor cold air box and special air tube.
    • High-lift camshaft.
    • Distributor with modified automatic advance curve.
    • Steel-faced cylinder head gasket.
    • Valve springs, cups and seats; various gaskets and hardware.

    Note that the Le Mans Kit did not include high-compression pistons that would become part of the 100M specification. Additionally, while Austin literature of the period claimed a power increase from 90 to 110 HP for cars fitted with the Le Mans Kit, an Austin Engine Test Department Power Curve chart of the period, reference No. SL6044, showed that a car fitted with the Le Mans Kit produced only 102 HP, or about 12 more HP than a standard car. Additionally, since the Le Mans Kit was sold as an aftermarket item, there are no records of which cars had the kits fitted. Indeed, standard cars can still have these kit components installed even today, and they will be no different from those that had them installed in the 1950s.

    Additionally, cars fitted with the Le Mans Kit do not include everything that a 100M has, because in addition to the components of the Le Mans Engine Modification Kit, the 100M also included:

    • 8.1:1 high compression pistons.
    • Race-type anti-roll bar.
    • Special-setting front shock absorbers.
    • Louvered bonnet with Le Mans-regulation leather bonnet strap.
    • Two-tone paint (in most cases).

    Note that the addition of the Le Mans Kit plus the high-compression pistons did result in a power increase to 110 HP.

    So the answer to the question, What is a 100M?, is simply this: The 640 cars that were produced and marketed as the 100M in 1955-56 are 100M models. All BN1 series cars, and all other BN2 series cars, with "Le Mans modifications," although perhaps largely similar in specification, are simply standard cars that were retrofitted with equipment that was sold separately, and the installation of that equipment could have occurred at any time from when the items were first introduced to the market, up until the present day.
    Last edited by Editor_Reid; 12-29-2016 at 02:25 AM.


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