Any belt that can be found to fit flush into the alternator pulley, is isn't strong enough for the rest of the system and will fail as well. I also tried adjusting things by adding washers and it made no difference what so ever, nor does the belt tension, by it too much or not enough. Bottom line is if a belt goes on, it WILL break off, it's just a matter of "When". I'm going to make my third and last attempt to talk to the jerks at Fluff Guff, this time with some links to your quotes on the forums here, that pic that you posted which also looks exactly the same on my car and some pics of my own showing the difference in size and fit. If they're still not willing to do anything about it then we'll see if the Better Business Bureau is. By the way, did you ever solve the problem? If so, how?
Hey bro, I realize it's been some time since you posted about this, but it's how I found you.... I too have the exact same problem with my "Tuff Stuff" alternator on my '68 and have also contacted the company who has been less than helpful about this and refuse to lift a finger, despite the fact that the groove in their pulley is CLEARLY too small for it's advertised application. Sure, "when" it works, it works great, but all I know is, I never broke belts before I installed this alternator and since, it's been literally hundreds of dollars in belts, one after the next. And I've tried every kind of belt under the sun, with perforations and without.
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