Effect of diff. rocker ratios on cam duration

Is there a way to calculate the change in .050 cam duration with a change in rocker ratio? I am working with Ford 1.43 and 1.54 ratio rockers.
If the relationship is a direct proportion (dont know if that is true), a cam with 240 duration using 1.54 rockers would drop to approx. 220 duration with 1.43. Right, wrong?

 

Lift will change ,the duration should stay the same. Multiply the lift by the ratio of the rocker arm.

 

Lots of good info. on this_thread for you to check out.

The quick version is this, the rocker ratio changes lift. The actual cam lob lift multiplied by the rocker ratio gives you total lift. (Ex. .326 cam lift x 1.5 rockers = .490 lift. .326x 1.6 rockers = .522 valve lift.) The durations, as I found out on that thread, changes very little to none. Hope this helps.

 

Duration at 0.002" wil be minimally affected. The more important number at 0.05 will be affected slightly. Because the profile of the lobe has some affect in the final number, there is no calculation to determine the change. You will need to install the cam and degree with each rocker arm to determine the difference.