Many years ago GM released a PCV valve to solve the low vacuum issues on their high performance engines in the 1960's. 

It is a fixed orifice PCV valve. It has a small hole in the bottom that regulates vacuum at a fixed rate. The part number for this PCV valve is GM part number 12572717 and you’ve probably seen this referenced all over the internet while doing your search for oil control issues and low vacuum problems.

GM part number 12572717 has been obsolete for a number of years now. This PVC valve is an aftermarket reproduction of that same PCV valve.

The body id 3/4" diameter 3/4" long to the seat. The other end is sized for 3/8" hose. The overall length is 1 5/8".