i have 300-350hp 355 it only has one belt for the fan/alternator and at higher rps the damn belt keeps coming off no matter how tight it is,any suggestions?

 

is it lined up properly? not angled by the slightest? is everything bolted down tight?

 

looks like its lined up perfects and i cant find and bends in the pulleys........

 

With the belt off... is the alternator and/or fan pulley spinning as freely as it should? A lot of resistance would cause the belt to "vibrate" I guess... it could come off that way.

 

im assuming that this is V-belt. If the alt belt keeps tossing, how is the belt to the power steering, assuming you have that on?

 

Yes it is a V belt,no i do not have the power steering hooked up, just alt/wp so far i have changed the water pump pulley,the alternator,tried a longer spacer behind the long alternator bolt, tried shims various ways,bought a new belt,im really running out of ideas...........

 

Not to be a smart@$$...

Here's one, convert to serpentine pulleys, you'll never experience
a thrown belt again! DUECE

 

I had that problem last summer.. when you tighten the alternator down, grab the alt pulley and pull it out toward the passenger side (twisting it a bit) that helped me some, but it still occasionally comes off. I'm still working on that problem too.

 

Not to be a smart *** but fed ex me 350$ for a nice set of underdrive pulleys and ill be sure to put them on.
Seriously though 350hp and 400fpt should'nt be too much for a v belt,.

 

Good one, and your right,... just a thought.
Hope all goes well in fixing the culprit.DUECE

 

Check your components for excessive play. I had an alternator with too much end play last season (long story) and went through 4 belts in one day.

Bent/warped pulleys will also do it.

 

This is not an uncommon problem around here either and we have theorized that the notches under the belt trap air between the tight curve of the alternator pulley causing hydraulic action to barf the belt no matter how straight the pulleys are in some cases... This may sound a farce but I now use a Dayco Top groove belt and voila the problem dissapeared. 6500 rpm no problems now ever four years and running. One other solution a stock friend uses is a deep groove pulley found on some older truck engines. Good luck!