here is a photo of a homemade valve to piston checking tool that i came up with.

it is for use with a hyd cam and stock rockers with light to moderate size springs and you don't have to remove the valve springs to use the tool.

just mount it in place of your stock rocker arm shaft and use a pry bar to force the spring down and use a dial indicator on the spring retainer to measure the distance of travel as the valve hits the top of the piston or when you get coil bind.