America Gets Supercharged
If you read The Rodder's Journal #29 on "The Italian Blower Story" - you'll learn that after WWII, in the early 1950s forced induction really became revolutionized by European manufactures like Italmeccanica. At the time, some enthusiasts were chasing exotic fuel mixtures. Others were playing with the stock valve trains to improve the breathing potential with aftermarket or custom made heads combined with high lift cams, like Ardun for the Ford, or the Wayne for the Chevy.
One approach to improve power was to install a centrifugal supercharger, like the kind you would see in prewar cars made by Graham, Auburn, and Cord. The benefits increased power from an otherwise unchanged engine. Centrifugal superchargers work well, but have some drawbacks. They produce good power, but not across the entire RPM range.
In Europe, supercharger developments had focused on positive displacement blowers, typically referred to as a Roots blower. Instead of an enclosed fan-style blower - a Roots-type blower used rotating and interlocking lobes to move air the air/fuel mixture.
Forced Induction in America
On the dry lakes, amongst the SCTA group, several racers had taken note of the Europeans' racing success, and had started to adapt Roots-type blowers to their engines. Some of the best known are Don Blair, Barney Navarro, and Tom Beatty.
The press helped spread the word too. Motor Trend magazine called supercharging "Harnessed Dynamite" in a 1951 article. A Hot Rod magazine article from April of 1952, titled Packing the Punch in Your Powerhouse, noted a 62% increase in performance to a stock 1950 Ford.
An Italmeccanica blower cannot be described as anything but a beautifully crafted casting - it is also said that beauty is only skin deep.
Italmeccanica blowers had some durability issues. Customers' frustrations ranged from decoding the instruction manual to the difficulty of finding replacement hardware which could either be metric or Whitworth, a unique English thread. More seriously was a factor of poor engineering, which had been noted in a 1952 Hot Rod article.
Many problems were traced to a helical (curved tooth) gear set used to spin the two rotors, made from a soft metal. The gear would fail under stress, and when a tooth broke, it could split open the case as the gears were forced apart.
Perhaps because of these problems, the Italmeccanica Company in Italy went through a business reorganization. A new company emerged called Societa Compressori Torino who acquired all of the rights, engineering staff and production facilities from Italmeccanica. The new company announced that the Italmeccanica blower had been updated and would be marketed under the name "S.Co.T.