Splash, I designed the system on the 37 after the photos you posted of the PCV on early GMC engines.
On the PCV valves, the one on my 51 truck now uses a valve from a 2.8 Chevy V-6, the 250 valve created too much suction in my opinion on that engine which has 20 inches of vacuum at idle, the 37 engine has 17 inches with it's hotter cam.Purolater PCV valves are marked by flow with a letter on the valve,other brands seem to use one size valve for many applications.
The valve needs to create a negative crankcase pressure at idle, but not too much, it's a trial and error situation, playing with a handfull of two dollar PCV valves.While my 4.3 powered S10 was idling, I placed my hand over the ventilation air intake on the valve cover, then pulled my hand away and listened to the "sound" of suction. I then duplicated the "sound" on the two Stovebolts.Crude home brewed engineering that works well in my opinion.
