I seemed to have just developed this problem on my 454. i have been keeping the revs to about 5700 rpm. starting to shift at about 6K and tossed the belt. right now am running the stock LWP 325-350 hp pullies with a deep groove alternater pully. I also have a chrome alternator pulley. what i would like to do is order the stock deep groove crank and water pump pulleys and perhaps a new belt. also put the stock alternator bracket back on. my concern is how the quality of the aftermarket deep groove pullies. i'm figuring about $150 for everything thru ground up but with the known quality of the repo parts i have some concern. thanx mike

I had a similar problem, and tried almost everything. Since I don't have a digital camera or a way to post a photo (and Im somewhat
"computer stupid"), I'll try to explain what cured my problem, so bear with me here.

Started with a piece of 3/4" x 1/8" flat stock about 2 1/2" long, bent it 90 degrees, and welded it to the lower alternator bracket. Now, welded to that, is another piece of the same stock about 2" long, which is positioned parallel to (or under)the belt, with about an 1/8 clearance between the steel strip and the belt. Finally, the leading edge of the strip in slightly bent down and smoothed out so that it will not fray the belt if the belt "flaps". graemlins/thumbsup.gif

(e-mail me if I did clarify myself too good)

You most likely have a pulley that is slightly out of alignment.

Take a small red laser pointer pen light and lay it on the water pump pulley.Now rotate the pulley so that the pointer light is pointing at the other pulley.Note where the light is centerd.If it is dead middle you are ok.Pepeat the same procedure with the next pulley.
If you notice that the pointer light is not centerd in the middle of a pulley you will need to shim it one way or the other to make the pointer light hit dead center.

Next get a new belt.
There are two belts that are very good with higher rpm applications that will stay put.They are made for just such an application.

Dayco Top Cog and the GoodYear Gatorback are the belts to get.Both of these belts are used by NASCAR.

Keep in mind that even they will be thrown if your pulleys are not lined up correctly.

If lining up the pulleys and installing one of those belts doesn't work you will need deep grove pulleys.
But is most likely that the process above will work.Worked for me graemlins/hurray.gif

Ratuned, I had the same problem that you are having with my BBC 4 speed. Everytime I got the engine around 5700 rpm or so, my Belt would end up hanging around the water pump. I did every thing, from checking the alingment of the alternator, by deep groove pulleys to tighten the HEll out of the belt with breaker bar. End result... Thrown belt.

Finailly, I identfied the by problem by the classic way of "rev Tuning" the motor. Once I got the engine around 5700 or 6 grand, while I was under the hood. I droped it down to idle (as in shifting) and then brought it back up to about the same RPM. I then notice on the bottom side of the alternator. The belt was creating like an S shape as it came off the crank and on to the alternator.

Solution: I roved the local junkyard for an idler pulley. I pull one off a old 70's toyota. I attached to an existing hole in the bottom alternator bracket and I havent thrown a belt since.
I hope this can be of help to ya. graemlins/beers.gif

I used to have this problem as well, bad alternater, after an alternater rebuild the belt has not come off.

HG

I noticed the same thing with my 454.
Big S generated at rpm change.
I spent hours linging up pulleys.
Put a deep V on.
Got gator back belts.
Nothing worked.
I made a belt guide that is almost impossible to see. Bolts to the lower alt bracket.
No more problems.

Dave