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?