i used a set a while back. when 440 source first came out wittem. they were my customer's idea, and his engine so i used 'em under slight protest. they've got about two years of service on 'em with a mild flat tappet solid cam, aboot .600 lift, no probs yet. the shafts were filled with polishing compound, and i had to pull the plugs and clean them. what a mess!