2003 Altima 2.5 Newly rebuilt Engine clattering on start up when cold. Continues until oil pressure light goes out ( Approx 1-2 sec.) Only on first start of the day all start ups after that normal. Oil Pressure 50 psi. Replaced oil filter with OEM filter, using 5w-20 oil no help.No apparent plat in rods or pistons. Checked Valve Clearances and Timing Chain and Guides and Balance Box Assembly no Obvious Problems. Should the intake Camshaft Varible Timing Hub have any rotational freeplay in it? It has Approx 90 to 120 degrees freeplay with timing chain removed . This is the area where the sounds seems to be originating.