I just got my ATI neutral balanced 153 tooth flexplate, for my internally balanced 383 LT1. How important is the guide/alignment pin? The engine builder didn't install a new one. Should I use the old one, or is it just there for the people at the factory to throw it on quicker and not put a bolt in the wrong hole? I mean, the center is hubcentric (tight) on the crank, so as long as I put the 6 bolts in the right 6 holes on the flexplate and the crank, does it really matter if the guide pin is in the other hole?

 

If the rotating assembly was balanced without the pin, I wouldn't install it. Just be sure the flexplate is bolted on with the holes for the guide pin lined up.