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Discussion Starter · #1 ·
I recently put a nice shiney March alternator bracket setup on my 302, which eliminated that huge donor bracket (which was kinda ugly), but also eliminated the spring-loaded belt tensioner. The March bracket comes with one of those screw-shaft type belt tensioners. Works fine, but they don't indicate how tight the belt should be.

If I remember correctly, in the days of V-belts, you tightened the belt until you could finger-press 1/2" of deflection on the longest run. However, I'm not sure if that same rule applies with serpentine belts. Due to their width and many ribs, I believe they have less slippage than the old V-belts had, so maybe they require less tension?

Thanks,
John
 

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I installed a 'Vintage Air' system with the same screw-shaft type belt tensioner. My instructions said to tighten the belt until you can barely turn the longest run inside-out if that makes sense. Unfortunately, the recommended belt was too tight to put on and the next size up was too loose when fully tightened. I'll experiment with it later. I found this link explaining belt tension for any belt length but you need to have a tool.
 

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Official OLD GUY
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Old school

says that the belt should not "flex" more then 1/2" total . . . but I [personally] have always used the procedure mentioned above. Tighten it until you can't turn any auxillery pullies by hand and then, if you are using one of the tubular style adjusters, turn the tube 1/2 turn more. Then see if the longest run can be flexed 1/2", just to make sure.
Without the proper tool to use as a reference, this method works 99% of the time.

HTH

Doc :beerchug:
 

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John,

I used the March bracket as well, and tightened until I had some deflection. Not sure if it's 1/2", but probably close.

Rob

 

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Torque Junkie
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Mine is like Rob's picture. I can just turn the long run 90 degrees. Or just tighten it until the belt quits squeeling everytime you turn on the AC. :)
 
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