I have some 1.6 rockers on Edelbrock heads on a 360. No complaints here good fit, good alignment, no trouble. If I had to guess I would say I have 150 or so passes on them, I don't keep track really. They have held up well with my .650ish solid roller. I think they have about 5000-6000 miles on them now, three drag weeks and plenty of in town miles.