Since I acquired my 1947 Packard Super Clipper with the 356 CID engine 2 years ago it has a loud tapping sound once the oil gets hot.. I am assuming it is a stuck valve lifter as it is coming from the area of the valves. I tried using a stethoscope with inconclusive result so I am open to other suggestions. The car has been driven probably less than 50 miles per year for at least the past 30 years. I removed the oil pan and cleaned out the sludge and ran some engine flush in two oil changes. the engine valve gallery is very clean now but the one lifter persists in clattering ( unbecoming of a Packard IMHO). A couple of people have suggested putting a quart of ATF in with the oil as a possible cure assuming of course it is a sticking lifter which is the problem. I know this is an old mechanics trick but have never tried it myself but was wondering what the members of the forum think?