I have two: The first is the back intake bolt on the 289 in my Cougar. When I removed the cast iron piece to put the aluminum intake on it, I twisted the head off. I bought a set of bolt extractors which got it out, but I was sweating every step of the way. The second was the crank snout on the 318 in my stepdad's Duster. When I pulled the balancer, the "snout" on the balancer puller buggered up the first thread. Again, an easy fix. But at the time, a major p.i.t.a. Wait, I though there were only two. On the same engine, the wet bolts that go through the timing cover were seized and I destroyed the timing cover trying to get them out. An hour drive and $20 later, I had a new one. Still, it was another inconvenience when trying to disassemble an engine. It's ESPECIALLLY true when you are making progress and don't want to stop to drive 30 miles into town to get a replacement.