Replaced all of the bottom 6-point nuts with the 12-point nuts. It was as expected and took a lot time. Had to remove muffler, intake and exhaust pipes, remove the 6-point nuts one at a time and replace each with the 12-point nuts. Then I had to reinstall the intake and exhaust pipes and the muffler. I’m still not convinced that it was necessary, but I should be good for another 544.6 hrs. before I have to tear the engine apart and replace the through bolts.
