The GM PCV system was created for trucks working in a nasty and dusty environment. Originally it had nothing to with the Clean Air Act or laws in California. California air pollution got so bad that they enacted laws to address the problem. The program was Jan 1, 1964 through Jan 1, 1966. Most 1950 and later cars and trucks, in California, had to meet the requirements. The National Clean Air Act started around 1970 and was initially required on automobiles built around 1971. So, unless your 1958 truck came from California or is in the state of California, you don't have to have the PCV system (to my understanding which is always subject to correction). AC (AC Delco a GM subsidiary) created kits "CV" and "KV" plus 5/8" ID rubber hose to meet California requirements. Hotrod Lincoln was one who installed them (big Grin). I have the AC PCV catalog. Start with (
http://www.gmpartswiki.com/getpage?pageid=226190) to get the Ventilator Assembly listing and nearby pages for various fittings and the valve.
What is the original PCV system for a 1958 Chevy truck? It is subject to interpretation, and I would have documentation to support having what you believe to be an originally equipped engine especially if you want to compete in an original truck showing.
GM modified the road draft tube (Ventilator Assembly) to accommodate the PCV valve at the top of the tube. The road draft tube has segments inside to trap oil mist vapors and drip them back into the crankcase. In my opinion this is the best location for the PCV valve. I can provide pictures etc. if you want the "original look" but original parts are hard to find.
The PCV valve you select is rated for a certain flow and you may need to use the correct diameter hose or pipes to not restrict flow.
Having put down my hogwash in writing, I have to say the systems of the 50's, 60's and early 70's are nowhere close to today's modern crankcase ventilation. The biggest advantage of the old PCV system is to blunt the hot burning oil smell from wafting through the firewall and stinking up the cab BUT the is the nuance or general experience of owning and old Stovebolt.
