One of the students is freshening up a 292. He was putting the heads back together and broke one of the rocker shaft bolts off in the head. I figured he probably torqued it too much or perhaps and bolt was just fatiqued. Anyhow, he buys a new bolt to replace it and the same thing happens - he maintains he hadnt even torqued it to 10 pounds (not sure how he knows that unless that is what he had the wrench set for??) This is occuring in the same bolt hole, all the others went in fine? He ran a tap down the hole and the threads seem okay. Is this a common problem, are we doing something wrong, or is this just bad luck???