I had a similar experience a couple of years ago with a block manufactured in 2002. One of the long bolts that attaches the sump to the back of the block stripped at about 5 ft-lbs of torque. The torque wrench was set to 16 ft-lbs, this was the last bolt in the sequence, and I had just started to turn it -- it was barely more than finger tight -- when it simply continued to spin with no increased resistance. At the time, I attributed it to metal fatigue from prior sump installations over the years (I think this was the fourth time), or perhaps the machine shop had used that threaded port to hold down the block during a machining process and over torqued it. Annoying, yes, but easily repaired with a Heli-Coil. -John