i can't imagine any flat tappet cam lasting more than a few minutes without some taper. the low taper was to carry the extra spring pressure. this is one reason for the better rocker arms too. i remember back in the day busting so many of the 1968 rockers that i'd carry a small bag of them in the trunk. 6-paks had chrome stem valves too. factory wedge valves weren't very good for abuse so the chrome stem helped but didn't solve the erosion at the top of the stem were the rocker made contact. eventually the chrome stem and hardened tip ended most of those problems.