72 302 block .60 over 351 heads 270 cam. I had carb issues recently and installed a new holley 600cfm the 1850 model. Ran like a dream for about 30 miles then a knocking on the passenger side valve area. Pulled over and took the valve cover off and no obvious signs of damage. Put it back together and tried again on the hwy. same problem getting louder. The knock in the valve area does fluctuate with rpm change. Why would this pop up right after a carb swap, and what could it be? I'm running 6.5 of fuel pressure and did set the carb with a vacuum gauge. Any ideas? Posted using the Full Custom H.A.M.B. App!