They said the knock sound like it was coming from the bottom end. But like I said before I never heard anything and Ive own this el camino since Jan. 2011. Also I was thinking how would they know my rockers were loose I just took it in for intake gasket and timing. now all of a sudden I have a knock and rockers are loose. what gives sound like a rip off to me too. I wont be going there anymore. I will pick it up tomorrow.:dontknow: