You will need to have the rocker arms spot faced where the jam nut tightens down or they will loosen up every time you run the engine through it's cycle.



The top where jam nut seats will definitely need to be spot faced. Usually tears up the adjuster threads from cocking the jam nut onto the crooked face. Should only cost around $30/$40 to get it done. The old 273s are way better than the Chinese junk.