I have a spare 1939 216 that came with my 38 when I purchased it two years ago. I removed the valve cover the other day to have a look at the rocker arm. To my surprise I can actually move the valve springs around that aren't under some compression. I wonder how the motor ever ran like that!
In 1939, the valve spring pressures were set at 49 - 56 pounds with valve closed, 121-133 pounds with valve open. It wouldn't take much seat wear to loosen the valve spring, and since they are weak to begin with, I am not surprised you can move them around.
Thanks for those numbers. I was going to look them up but now I don't have to! So in it's last running days those valves would have been held closed by the compression It must have made quite a racket..