The change in valve duration is variable from .050 to max lift between the 1.5 vs the 1.6 ratio. At .050 its around 2* more difference with the 1.6,s and pretty much stays there duration wise on the lift ramp to near the top of the lobe.

As the lobe peaks things change, the valve duration increases more then 2*, actually a bunch 10*, 15* or more vs the 1.5,s. But its effects arent as great as the extra duration would suggest.

The cams effective duration is still only around 2* bigger at the base. Lets face it, if its a 250* duration cam, its still around a 250* duration cam. Its not no 260* or 270* cam.

A .600 lift cam may have about 5* of duration or less at the nose. With the 1.6,s youd have .640 lift at the nose. To scrub off that extra lift it could take a extra 10* on either side of the lobe before the lift see,s .600 again.

You got the Ramp up and the Ramp down, things at the very peak lift wise are moving slow. So it takes longer to move the valve thus creating the extra valve duration over the nose vs at the seat.

E Marine, see if your buddies know this. mike