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Join Date: Aug 2001
Location: Mason, OH
Posts: 2,568
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Alternator Belt Shimming Question
I put 2 new belts on the 911 today but after doing so I have a shimming question for the experts relative to the alternator belt...
to get the proper tension (about 1/2" deflection at the mid point of the belt) I used 2 shims between the pulleys and 4 on the outside between the washer and the nut. Other information: in addition to using 6 shims in total, I used the 10x710 belt and torqued to 40 NM per Wayne's book. Seems strange to me to only use 2 shims on the inside of the pulleys and have 4 on the outside but when I tried 3 and 3 the belt felt too loose (almost 1" of deflection). Does this seem right to you or did I do something wrong? My other thought is that maybe I will need to readjust the belt (ie., add another shim inbetween) after a few thousand miles when the belt stretches. Comments and/or thoughts? TIA
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Doug '81 SC Coupe |
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Doug,
Sounds fine! I have encounter several belts that only needed 1 or 2 shims between the pulley halves. Only thing is ... you should recheck the belt tightness in a week or two, 500 miles, maximum! Then, after the belt is broken in ... it will have stretched a little, so you will need to take out a shim or two, and move it/them to the outside with the others!
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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Hey Doug!
Good to hear from you. I was going to respond but Early already hit the nail on the head. It's not unusual. Like he said you may even need to take one out after a few miles. Rob |
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Join Date: Aug 2001
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Thanks for the quick response guys. I will definately recheck the deflection in about 250 to 300 miles.
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Doug '81 SC Coupe |
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My wrench informed me that authorized Porsche belts are actually 9.5 rather then aftermarket 10". This would explain these belts needing only 1 or 2 shims between the pulley because of the increased length. Also remember to keep turning the fan blade when tightening to prevent impinging the belt when torqueing.
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Join Date: Oct 2000
Location: Sherwood, Oregon
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I think the 9.5 is the width. 9.5 cm by 710 cc. But all you can find is 10 cc. A little wide. Tried to order straight from Continental. I can't get mine to stop from whining at launch.
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Cary 77 Carrera RS w/3.2 #59 73 914S 2.0 AG 73 914 1.7 Driver ( daily driver, under complete rustoration ) 74 914 2.0, 71 914 Tub, 74 914 2.0 Tub + 73 914 donor |
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