Had a client looking for a shop to weld a broken stud on the block onto which his starter was boleted. I did not want to do it and recommended JB Weld. Am wondering if this is the best solution to the problem.
I would not want to preheat a block, no matter what.
From the OP, it sounds like the STUD is broken, not the block. Proper repair is to remove the stud if possible or drill out the stud and re tap using a helicoil or bushing.
Best solution if you don't want them to come back maybe. Although, from my experience recently the cost for you to actually weld, tap the block costs multiple times more than a single tube of jb weld. Which means they wouldn't want to pay "that much" and jb weld would be worth a try. LOL!!