In a recently purchased 1963 Thunderbird with a rebuilt 390, when the RPMs get up high enough there was a knocking noise from the front of the engine. Upon stripping it down and getting the timing cover off, it's evident that the timing chain and fuel pump eccentric have been hitting on the timing chain cover and have worn in grooves. This is only at the top of the camshaft timing gear. I assume this was the knocking noise. Why would the timing chain and eccentric be eating through the timing cover?