Dodge: 3.0L valve sounds

Hello,

One of my friend has a 91 minivan with 3.0L engine in it. I noticed
that it has a very bad valve sounds. They hit the head like crazy. Can
the problem be fixed without removing heads, or should he remove the
head and machined it. I mean is there some shaft or larger rocker arms
that can fix the problem without costing lots of money.

thanks.

I will try to change or clean the lifters. If helps, i save alot of
time, or next weekend, I will start tearing apart the head.

what are the specification of the camshaft thickness, or any way if i
can tell rocker arms are still good.

Thanks.