I recently purchased a GM deep groove alt pulley because my engine will throw the fan belt if its revved high. I removed the old pulley and installed the new one and to my surprise it seems it was machined incorrectly. When you spin the alternator the belt groove moves forward and backward. I called Ausleys and they sent out a new one and it does the same thing. Why is this? The new pulley has a keyway which I don't need but it's otherwise a slip fit. Has anyone else used this pulley? It's about 3.5 inches in diameter and it's cut from a solid piece of steel. I've seen the same part in the Year One catalog and they say it was originally installed on the '67 396/375 engine. Any reason why it won't fit a '70 454?

Bill,
Some thoughts.... I have been through belt throwing hell and my final solution was to put on a Jeg's low mount alterator with East Coast alternator and voila, all my problems were solved. But that is another story. I tried everything everybody told me including
1. Try differnt brand belts
2Try different diameter belts
3 Try smooth and ribbed belts
4 Try any combo of all of the above
5 Use a straight edge to make sure the alignment is ABSOLUTELY PERFECT from the alternator to the water pump and from the crank to the alternator.
6 Shim the alternator to make the alignment correct
7 Have someone rev the engine and watch where it gets thrown from. Mine oscillated from the crank to the alt and threw it but some throw it from oscillation from a fifferent area.
8 What have you changed to make it start throwing now? Retrace your steps.
9 I never could fiqure out why mine suddenly started puking belts but mine is a race car and I eventually came to the conclusion that the stock set up just wasn't meant to handle 6700 rpm shifts on a routine basis
I hope this has helped
Please let me know what you find out as I am curious whether I overlooked something.
Michael
PS You said "deep groove" . I am unfamiliar with the pully you are talking about but somtimes "deep groove" pullys are a different diameter than stock and can cause charging problems.

Thanks Michael. To answer your question, I relapced my belt-throwing 350 with a 454 which can rev a little higher but the problem persists. Everything is in alignment and tight.I would like to hear from anyone who has a factory-equipped solid lifter engine. It should have the same pulley I now have.(I know you guys are outhere I have seen you refer to your L78, L89, LS6) Has anyone had to remove the pulley for any reason and did it use a key to keep from spinning on the shaft. Thanks in advance.

Guys I solved all my belt throwing problems by using a March underdrive pulley from Summit. The belts think they are only doing 4500 rpm at 6000 rpm

On our old '69 427 car, which had the stock GM deep groove pulleys, the only problem I had was rolling the belt over occasionally at high rpm. This was after I had removed the smog pump. With the pump reattached I had no more problem running up to 7200rpm. The long distance between the alternator and the crank pulley seemed to be the problem area. An idler pulley to replace the A.I.R. pump is probably all that is needed. Triple check that the pulleys are lined up as well.

Bill, Genes answer with the March pulleys solved my problem on a 660 roller 454. The only other thing is to try is smooth rather than ribbed belts for they should not walk off as bad.Hope this will work.