340 Cam

I get that the closer to zero you start measuring duration, the longer the duration measure you're gonna get. But measuring from where the clearance ramp meets the acceleration ramp and then adding 4 degrees on both ends - never heard that one before. Interesting. Wonder why Chrysler did that? More accurate measure of effective duration? I.e., duration that actually contributes to airflow through the valves? Thinking that effective flow is practically zero during the clearance ramp?