How do you tell if a car has a solid lifter cam

[92646]

I know this sounds like a dumb one but how can you tell if a car has a solid or hydraulic cam. I know listen for the solids rattling but I am thinking the lifters could be so far out of adjustment that they are going to make noise no matter. I was thinking of pulling the valve covers and push on some push rods that have the valves open after the motor has been sitting a couple of days. I thought the lifters would bleed off if they were hydraulic. Any other ideas?
Mark Sheppard