There is a specific procedure for adjusting the lifters on that engine and it takes a little bit of experience to get it right. They have to all be brought to zero lash with the engine running.
That is done by backing each one off until it continually clicks and then slowly bring it down until the clicking just goes away, no further. You may have to do each one a couple times to be sure. This can be a little difficult with all of them clacking at once.
Once they are all at zero lash, then you slowly bring each one down the specificied number of turns which you need to verify but if I remember right, that engine is either 3/4 or 1 turn.
This is going to be further complicated by the oil spraying everywhere while your doing it. Don't attempt it without the engine running because the lifters have to be pumped up with oil for this to work. You can do a lot of damage to the engine if they are too tight.