I had a problem with valve train noise with my zz4.
You need to check the rocker studs make sure they are tight.
I also had a problem with GM and there warranty if you installed the engine your self it is parts only, if you used a certified GM mech. maybe you might get the full warranty if your dealership honors the warranty
My local dealership would not honor my warrantyGM wanted me to get the car towed 45 min. away.
Needless to say I have been band from my local dealership they claim I have a little temper.
anyone who is thinking about buying a GM crate engine read the warranty very very closely.