If some of your lifters were pre loaded or run in an engine the check ball will stop compression of the lifter the harder you push the more the check ball stops the oil from escaping! When the engine is running the check ball bounces off the seat for a split second at the speed of cam rotation letting it bleed and then it seats letting it fill (All during this split second) when valve spring pressure is released at the heal of the cam lobe! When pumped up with valve spring pressure on the lifter the oil in the lifter can not be compressed your hyd. lifter is now a solid! when it comes around to the heal of the cam and the valve spring pressure is released the ball comes off its seat and bleeds and seats and fills and starts its ride up the cam opening the valves ETC. So if the lifters are pumped Full of oil)you wont compress them by hand!! Try taking the stuck lifters and hitting the bottoms on a piece of wood it will make the check ball bounce off its seat and may let a little oil bleed off at a time! Do not bounce ( bang or hit) them an any thing hard it will damage them they only need momentum and a guick stop to un seat the check ball! If you don't under stand don' try it! What I wrote reads good to me but I know the procedure and did it through many years and I wrote it LOL
it may not make much sense to you! It may save you from tearing them all down! If the plungers are stuck or plugged this wont work! Then you need to follow Cobalt advice, and do some real work!
Let me know if it helps you!
P.S. I did this with Chry. & Ford lifters in the past because they are clearance checked completely compressed .