20-09-2017, 07:17 PM
Well, two suggestions. One is the rather drastic step of welding a 5/16 nut onto the stud,close to the block and hoping the heat makes it loosen. It sometimes works. But before you try that, locknut a pair of nuts onto the stud. Then with a spanner apply a cycling torque, to about the level you'd expect the stud to unscrew. Do this rapidly lots of times. With any luck it will work.