Here's a real world example of showing 1.6 and 1.5 rockers w/ the same cam, same pushrods, and same brand of rockers. The measurements were taken at the valve w/ the lash at .020" for 1.5 and .022" for 1.6.

Valve -- 1.6 --- 1.5
.006 -- 302.5 - 302.5 (SAE duration)
.020 -- 291.5 - 290.5
.050 -- 273.5 - 271.0
.100 -- 251.5 - 248.5
.200 -- 216.0 - 211.0
.300 -- 184.0 - 177.0
.400 -- 152.0 - 140.0
.500 -- 113.5 -- 95.0
.550 --- 90.0 -- 63.0
.600 --- 58.5

Peak Lift - .637 - .589

NOTE 1: The "net" effective change to the "duration at .050 thou" # measured at the lobe can be approximated by the increase in duration at the valve measured at .075". I didn't measure that lift value, but you can average the increases seen at .050" and .100" valve lift and come up w/ an estimate of about 3 degrees.

NOTE 2: If the lash hadn't been adjusted for the higher ratio, the duration would have increased from .006" on up because the lifter would have contacted the lobe farther down the ramp at the point when the lash was taken up.

NOTE 3: This is the cam I was using in the Challenger since having switched to the Stage VI heads. My cam, my measurements, my data, my analysis, (blah, blah, blah).

So, there's your answer. I'm just not sure what the question was...