I have a 1970 455HO all original w/ the motor rebuilt about 300 mls on it. Over a year ago I did a sprint on the hwy and took it up to about 100 mph. After I got it home I heard a slight tapping or knocking and thought it was in the valvetrain. Put a stethescope all over it and cant locate it. Felt it was a lifter and wanted to put in a Ram Air 4 cam anyway which I did. Lifters, cam, and timing set from Comp Cams. Still there. Never gets louder and I can't really hear it when I rev it. I have had rod knocks before and this isn't like that at all. And a rod gets louder when hot and worse over time. So I put STP honey and 20w/50 on an oil change which I figured would quiet it down if I was wrong and it was a rod and it is exactly the same cold and hot. No change. Well I had it on my new lift running and had the stethescope all over it again and the sound seemed to strongest at the fuel pump. So I figured I would change it out only $31.00. No luck. The essentric on the timing gear for the fuel pump seemed fine when I did the cam. Are there more than one size and mabey it's smacking the fuel pump arm when it rides around? This is now driving me insane. Any ideas or known issues? Help!!!!!!!