[sperry]

Originally Posted by Dean

Huh? Fasteners do not normally define the torque, the materials you are fastening, or the tolerances in the parts determine the torque. Otherwise you have failures like this, or deform parts in a manner which might contribute to failure.

I agree with the cause assesment based on the damage, but the fault lies in the higher torque placed on the fasteners, not the block materials or design IMHO.

Just beacuse you use a higher grade bolt/fastner in an application does not mean you increase the torque on the fastener. If anything, i would think you might decrease the torque as the fastner would have less stretch.

I need to go back to my college materials class...

I thought the fastener requires a certain amount of torque because lower torque would allow the threads to back out.

For example, a high-grade nut/bolt would require more torque than a lower grade because otherwise the threads would not stretch enough and therefore there wouldn't be enough friction to keep the nut on.