Just noticed this and wanted to know if anyone else's does the same? Blip of the throttle and watch the idler arm...I noticed mine kicks up and out just ever so slightly. Enough however to make a belt jump the groove and throw the belt. I was thinking it wasn't aligned (which by the way still isn't--blower pulley now) but now I KNOW for sure this isn't supposed to do this. Mounting bolt is locked down too, so what would cause this and how do you fix it?

Oh and has anyone had a steel bracket made? Thinking of doing this down the road w/ a few modifications to it.

Silas,

 

Yes, my app did... (97ss - 383 - D1 - M6). So I fixed it. I fabbed a delrin stop to limit the transient vibration of the idler arm (about 0.050" gap). It happed to me wen I went to a 7.6 --> 3.4" pulley ratio and the belt had more top side slack. When the blower unloads, the top side of the belt becomes the tension side. This sets up a cyclic vibration due to the blower load mass air movement. The ATI Procharger does not have any damping system and contains 2 springs. The arm can go thru wild cyclic amplitude. With a F1 step-up ratio of 5.4, it will be worse than my D1. Many people reef down on the spring, but, that just puts more overhung load on the crank snout. Nat a good thing for limiting fatigue failure. B. Hope this helps you.

 

Thanks B. I guess the pics you sent me a while back is what I need to do. Where did you pick up the delrin bushing? Sent ya another pm.

 

I made my own. Purchased 1/2 by 1" nylon or delrin/ acetal plasic stock. Machined the stop. Quite simple. The mount is on the water pump fastener/ bolt. Extended that fastener with a 3/8-16 stud and heavy flanged nuts. B.