My 91 has decided to start eating distributor caps. It cracks them every 2 or 3 days. Always cracks near #2 and #6 posts. I have tried factory parts and aftermarket parts, no difference. New rotor each time. Shaft feels tight, no slack there. Anybody got a clue on this one?

 

I bet your distributor shaft is worn. Take it out and inspect it. But be sure to note the orientation before you take it out!

 

It doesn't take much wear on a dist shaft to make it wobble. Just a few thousandths of an inch are enough to make your life miserable.