rocker adjustment

[epphx]

I have a chevy 350 stroked, and I had a machine shop build me a set of heads. I also put in new lifters.
I put them on,and adjusted the stock rockers by the book. It started right up, and sounds great except it sounds like the lifters are tapping against the cam, should I tighten the rockers more, or is it normal?
It didn't sound as noisy as this before, did I do something wrong?
and can I damage the cam if I go too tight?

would love some advise Thx Eric in phoenix