Can I ID a cam without dissasembling the engine?

I have checked valve lift off the pushrod (rocker arms removed) using a magnetic dial indicator. Some people will say a hydraulic lifter will compress, but my experience has been that a dial indicator will not compress the lifter bore. Your only other option is to take off the intake and insert a solid lifter or take a measurement off the edge off the hydraulic lifter. Don't forget to multiply by 1.5 to get your total valve lift.