340valve train noise with new head gaskets

i ran it with the gaskets and it sounds like a rattling noise,when it revs up its much quieter.its loudest at idle,i rolled the motor ove today and checked each pushrod on the flat side.they all spin easily and the rockers slide side to side easily,shouldnt the pushrods be tighter ?as the lobe comes up they get tight and dont spin at all.the pushrods lenght are 7.50 inches.