I bought my engine (396) from a friend who had it professionally rebuilt. It has less than 500 miles on the rebuild. I just got the timing/ignition/mixture tuned in last night. And now it has a slight knock that seems to be coming from the mechanical fuel pump. I'm not positive that its coming from the pump, but it sounds like it. When I got the engine from him he had a block off plate as he used an electric fuel pump. I pulled the plate off because I bought a mechanical fuel pump. The fuel pump pushrod was just resting against the block off plate. My question is, could this be causing the knock?