In many engines with high mileage, piston slap, or rattle can be quite pronounced when the engine is cold, and hasn't been run in awhile. Try adding STP oil treatment to your oil and see if it reduces the noise. STP has the ability to cling to engine parts, not run off when hot, and fortify the oils ability to lubricate your engine during these periods of storage. And have the timing checked, it could be ping from poor fuel. a mechanic can verify the timing for you.