96 5.7 Valve Tap

I have somewhat of a problem and i am hoping someone will be able to help me. On my 1996 Suburban, 5.7 liter vortec, 4X4, auto, I am hearing what seems to be a valve tap on the drivers side. It is definantly coming from the top of the engine, and when i take off the oil filler cap and put my ear to it, it is very apparent its coming from in there. It is a slight tap, similar to that of an exhaust leak. The previous owner recently had the heads remachined, and he installed them himself. My question is this. What would be the correct procedure for finding/tightening my loose valve? Can i just pull the valve cover and tighen up the loose one or is it more complicated than that? I apologize for my lack of knowledge on this particular subject, any help is appreciated. The engine runs great, no problems, the only thing i notice is an oil smell after running it, but i suppose im just paranoid. No codes either however i have got a code P0430 that has gone away with a code erase. Also i suspect there may be a little leak in the exhaust system. Something i will get checked out next week. 3 of the 4 O2 sensors are brand new. Thank you for any help!

The engine has to be running to adjust valve clearance. To do this, you have two options:

1)buy a set of junk covers. Drill a hole in the covers over the rocker arm nut big enough to get a socket in there. I would use a deep-well socket on a locking extension to eliminate the possibility of droping the socket in.
2)get oil EVERYWHERE

I would go with option number 1. Start the engine and back off the first nut until you get more ticking. Tighten it down until the ticking stops, then tighten it one more turn. If I remember right, the book says 1/2 to 3/4 turn, but with hydraulic lifters, a full turn will be fine. Repeat 7 more times.

An exhaust leak can cause po430, also if the heads were machined the valve adjustment should be on the low side of the spec so as not to bottom the plunger in the lifter, 1/2 turn.