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I got much of this information over a period of years, while reading about the new-for-the-U.S. Subaru WRX around 2001, and the various performance modifications available for it. I cannot remember exactly where I read the bit on racing during the 50s and 60s, but trust that it was a reliable source. I also followed the "harmonic destruction" controversy, which seemed to play out until there were "experts" on both sides of the argument. Probably the most reasonable conclusion came from a response to a letter to an automotive engineer (again I apologize, I forget what car company he worked for). He said something like: I don't know what might happen, but the crankshaft pulley was designed that way for a reason, and the risks are not offset by the gains, so leave it there... Even he wasn't sure.
I am removing the two external links cited as they are both for driving to a manufacture of under drive pulleys to sell product. If the original poster would like their sites included properly use your sites information as a reference source. Frequencydip (talk) 14:44, 27 October 2010 (UTC)