03 silverado 5.3 engine knock??????

have 03 silverado with 5.3 engine, 60k on it, has a knock at cold start until warms up any ideas??

It's normal and causes no harm to the engine. Some claim to eliminate/minimize it with different oils. If you want a little more reading, do a search for "piston slap".

ha, there is actually a site for this http://www.pistonslap.com./ I am a synthetic advocate but maybe running some non synthetic will fill the bore, or heavier weight, eh, thinking about it, it might not fix the slap :( so it just started at 60k? my truck is getting close to 60k

I would not use oil any thicker than 10w30. Using thicker oils will interfere with oil flow and the oil pressure will increase. In a worn engine it may be okay to increase the viscosity of the oil because the bearing clearances have become larger.