General Motors did a sneaky trick on my 37 Buick concerning valve noise; guess they didn't want a snooty Buick to be as noisy as the common Chevy. They draped a 1/2" or maybe thicker piece of felt over the rocker assembly which muffled it tremendously. With it in place it sounds like it has hydraulic lifters and without it clatters away with two more cylinders to rattle than a Chevy. Some of my machines have felt in the oil cups and very early cars used oil soaked felt to lube some components so I guess it was a common practice.

Evan