That thing got a hemi? Just Kiddin'. Check the hose and carb fitting for blockage. Also check the filtered cap on the other valve cover. If the vacuum gauge read a bouncy 18 a leak is likely, though it may come from the pcv. Try restricting the hose a bit until the rattle stops. If it all checks out try the suggestion at the end of this thread: https://board.moparts.org/ubbthreads/show...amp;Search=true
Say hi to Gail & the grandkids for me. Need to get down there for my parts and
Ron
P.S. if the link doesn't work do a search for "pcv valve"