View single post by Mark Rosenbaum
 Posted: 07-17-2005 05:16 pm
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Mark Rosenbaum



Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
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 Sometimes the bearings are still good and the whine is due to the belt becoming resonant due to tension changes as it ages.  I've had good luck by (a) setting belt tension so that it's possible to manually twist the belt between exhaust and crank by 45^, and if it whines at that tension, gradually reducing tension a little bit at a time until either the whine stops or the belt can be twisted more than 90^.

All the idler pulleys I've seen are slightly crowned, i.e. the center of the pulley has a slightly larger diameter than either edge.  As I understand it, this makes it less likely for a belt to walk off the pulley, and avoids the expense and weight of using flanges.

As I understand things, wear in the cam gears causes slight alterations to cam timing with respect to the crank and between the two cams.  This is due to changing the points at which the belt contacts the gear teeth, not changes in gear diameter.  It's not really a problem unless the wear rate of the timing belt becomes absurdly high, or belt tension drops so low that the belt can jump teeth.  This is a good thing, as the last time I checked, new cam gears from Delta were US $110 each.