The PCV valve comes apart. There is a valve and a spring inside. The valve has a hole in it. Sucking on either end you are sucking air through the hole. Manifold vacuum should open the valve. Take it apart and clean it.

Somewhere in the mid '50s they were changed from an oil bath breather to a paper filter one. That may be the smaller/bigger you noticed. The one on my Suburban is the paper filter one from a '59.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.