would bad rocker arm make burring sound just on left side of motor it is 400 small block chevy?

Bad rocker arms/lifters can make a ticking sound, however if there is a pushrod rubbing against the side of the head it can make a whirring sound, like metal rubbing against each other. I am not sure if the burring sound is a whirring sound or not, but if the push rod is rubbing, it means you have a problem with the rocker adjustment, or a failure in the rocker or lifter. If you are running a 400, it is several year old, so it would not be uncommon to have some problems with the valve-train. It is common to have partial failure of the lifters especially if you have oil sludge interrupting the oil supply for the valve train or lifters.

What should be done? Pull the valve cover, and check it out, start with simple, go to the more complicated.

Sounds like an exhaust leak! How is it running? if it still runs good I would take it to a mechanic. It is too hard to tell what it could be and needs to be heard by a mechanic. Those 400 small blocks are awesome engines!

Bad rocker arms 'tick'. Exhaust manifold leaks tick, too.