Like some of the others, I have also ran a solid flat tappet cam with factory adjustable rockers, with over .650" lift. t was an old Comp Cam, I believe the exhaust lift was either .678 or .687" lift. That was in the late 70s-early 80s, wasn`t a lot of alternatives back then.Never hurt a rocker arm but did break a few shafts, no end supports back then.