sounds like a valve knocking

I have a 2003, 1.8 dohc,automatic w/od. I pulled out on the highway and pushed into passing gear to get up to speed. Then I started hearing what sounded like a valve knocking against the piston. Pulled the valve cover didn't notice any visual problems. I need to know how to check timing in relation to cam positioning....any advice...I think it might have jumped time but I'm not sure of the cam postion. I already have the crank at TDC