Do you think I got screwed, or is it just part of the hobby?

Thanks for the replies guys you are making me feel a little better. As far as the oil and noise, the oil I have used has always been 10W 30 Valvoline VR-1 Racing Oil. I have eliminated all the possibilities I can think of with the knocking/rapping noise. Pulled the dipstick while it was running, no change. Checked the entire top of the valvetrain while turning it by hand (which was what I assembled), everything is good up top, and it is definitely louder underneath the car by the pan