How much time you have on the engine?
Hydraulic lifters when at a static state the inner plunger/cup should have a little movement up and down with some resistance, this is the internal spring returning the cup back to the extent of travel. Once the lifters are pressurized the resistance becomes greater due to hydraulics, hence the name. If you have lifters that the inside won't move freely then there's a good chance their full of crap and can be cleaned and re-used if the wear isn't abnormal. I always change my lifters when I rip into a engine because they're not all that expensive and it's cheap insurance... but that's just me. Before anyone goes postal, it's acceptable to install new lifters with a used cam but not the other way around. If you do have the chance, change the timing chain and sprockets as well if your engine has some miles on it. You won't regret it..