I'd do the simplest thing first. Take off the valve cover and re-adjust your valves. They also have several products that you can add to your oil that may help. Sticky lifters usually refer to hydraulic lifters not solid ones. I have a feeling your oil is getting to dirty and or to thick. When it warms up the oil thins and the oil flow more freely thus no noise. Once you take the valve cover off, you'll see how much gunk you have on the valve train. Cecil...