fan belt question...

[biosurfer1]

i have a very annoying problem with my fan belt, it seems fine until i get up to about 3500 rpm's and then it starts to vibrate pretty bad and makes a loud niose throughtout the car, it seems like the belt it pretty tight, but is there something i'm missing? and suggestions on how to make it start?

TIA

[no substitute]

Vibrate how? What type of noise? Does it deflect properly according to the sticker in the engine bay? What year 911? Are all your shims in place?

[biosurfer1]

its a 1979 sc, it got dark before i could check the shims, i never have before, i dont remember there being a sticker about the deflection, is it a universal number that i could find somewhere else? i would assume that it is more than there should be.
i think its the deflection causing the noise, but it sounds like someone if vibrating the car, kind of hard to describe...i'll check the shims tomorrow morning, any other ideas?

[Wil Ferch]

Yes.....you may have to take the front-half of the (upper-fan) pulley off to check...but the "oblong" cut out of the pulley and/or the oblong raised portion that it sits-on...may be damaged and doesn't allow the pulley to retain a hubcentric "center".

First....check for proper belt size ( for 79, forget....either 710 x 9.5 or 725 x 9.5). Don't use the 9.5/10 "universal" type size belts for whatever the right size is....

Wil

EDIT: use 6 shims total...for those not used to establish tension..place them under the outside nut...don't discard or fail to use all six.