Valve Adjustment?
 

I have a 1990 Ciera, 3.3L V6, and recently had the head gaskets replaced.

The problem is, the first cylinder has a valve adjustment problem. I've done it twice now and it just becomes loose and begins knocking.

I've also notice the car hesitating a bit when accelerating. And the vibration, when in gear, is strong.

My questions are, I've asked a mechanic about the valve problem and he stated that I needed new rocker arm nuts. Is this true?

Thanks a lot.

[It's becoming a real pain when the rocker arm nuts become loose]