1998 Chevy Blazer LS, Install rocker arms and pushrods, torque rocker arm nut to 20 lbs to spec. but the pushrods are tight. Pushrods can not be turn back or forward is this right or wrong. Please let me know

 

If the lifter is off the base circle of the cam, there will be valve spring pressure on the lifter/rocker/push-rod. Perfectly normal. You can rotate the engine over checking each push rod as its lifter gets to the cam base circle and it should spin with some resistance.