Thread: older dart 360 heads
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Old 04-16-2010, 07:06 AM
  #3  
zipper06
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Join Date: Jan 2006
Location: La.
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It comes from the heat, when the heads are first cast, they are heat treated, then machined. After yrs. of use and the constant heat ups and down it draws down the temper of the alum, making them get softer.

JMO

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