Have you pulled the valve cover to ensure there is oil getting to each rocker? If not, that would be a very worthwhile thing to do. If putting Rislone in the valve cover stopped alot of it, could be they are running dry.
A few friends of mine put together a nice how-to for valve adjustments (yes they are the same thing) here:
http://devestechnet.com/Home/ValveAdjustYou need to know if you have hydraulic or solid lifters to proceed.
