vw type 1 technical vlog 18.5 hvx mod grooved rocker shafts and lifters

most of this discussion is about the grooved lifter so i will refer to this mod in this vid as the hoover mod. if you don't want to see math and a spreadsheet then this one is not for you. the deeper you go into this set of mods the tougher they get to analyze. thus the math and the extended discussion which results in a long video. it could have been longer. i took even more relevant discussion out.