Originally Posted by RED DOG

RED DOG was right about this one!
But I'll give this one more try. It seems that the mechanic friend here is tripping on the minor difference in the gap when he spins the pulley around. Yes, perhaps he either needs to add or remove shims to get it closer to spec., but my experience is that the gap will vary slightly. Unless the pulley clutch plate on the pulley is warped out of flat, there is no need to "trip" on it. What's important is that it clamps down flat with no gap when it is energized(no space for feeler gauge anywhere all the way around), that will let you know if the plate is warped. The electromagnet is energized and clamps down the pulley clutch plate at around 2k rpm, or sooner depending on the engine load. So the insignificant imbalance of the pulley clutch plate never gets to the high SC speed, because the minor imbalance disappears when it clamps down to the electromagnet. If all this is true, you can put the belt back on and drive it.