To the best of my knowledge, there are no pulleys for the M271. The supercharger is supposed to be operating near its maximum rpm on this engine. If that is true, turning it faster will cost hp, not make more. Also, the M271 uses a single belt to drive everything, so a larger crank pulley would turn everything faster, using more hp. People who have measured clearances say the crank pulley can't be made larger without hitting the water pump. It is not possible to fit a smaller pulley to the supercharger due the the design of the pulley and drive shaft.
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