Could be the post I did last season when I had a HS rocker break on consecutive weekends, first was #3 exhaust, next week #4 exhaust broke. No apparent cause and Randy at HS told me that it was most likely due to them reaching the end of their service life. Had a friend who's a metallurgist do an inspection of the broken arms and he said he didn't find any evidence of stress cracking. I also discovered that the roller lifter tie bars for each of those cylinders had broken, which begs the question, what broke first, the lifter tie bar or the rocker? I've replaced all rockers and lifters for this season so we'll se how it goes, if I can ever make it to the track!
