valve train noise

I have a 2001 cherokee Limited with the 4.0Lt power tech engine. Sometimes it makes a faint clicking noise like maybe a lifter sticking a little, or maybe the rocker arms need adjusting.Question can the arms be adjusted on this year, or some type of additive i can put in the oil to clean the lifters up.When you have the hood up you can't hear it.Mostly from inside the vehicle near the firewall. It does'nt do it all the time, just once in a while.I use 10W30 oil and have 60,000 miles on it.Maybe I should just turn the radio up louder.Otherwise this is a super running jeep. Thanks for any suggestions.

some knocking is common, usually in the bottom end. easy suggestion is use 10-40 instead.