Since the '51 will be in a few parades this summer, I decided to see about trading the road draft tube for a PCV valve. I started with this and modified the install a bit. I used metal fuel line from the intake manifold around the front of the engine, then used rubber hose to connect to the PCV valve. I also used a grommet inserted into the draft tube hole instead of a freeze plug. Also, my tubing wound up being 5/16" instead of 3/8". Everything seems to work properly, but I am wondering if the system will provide enough ventilation at highway speed. I started the truck, and removed the vent on top of the valve cover (oil filler). When I put the palm of my hand over the opening, I felt a gentle vacuum. I just want to be certain that it is enough. I don't want to blow out seals or worse. Has anyone around here done this conversion? Paranoid or cautious...you decide!
Posative Crankcase Ventiation You'll find you use less oil than now if you move the PCV Valve up to the intake manifold , there's WAY too much oil splash down there , the GM Factory PCV Valve holders were inverted & baffled Road Draft Tubes in the beginnng . I have at least one kicking around my back yard . The PCV Valve does nothing above idle speeds , it's designed that way . The test you did , is the old Dealer Test , we'd take a shiny bit of paper (Magazine Cover) & place it over the oil fill hole instead of the cap , if the vacuum was sufficient to hold it from being blown off by the fan's prop wash , the PCV System was in good working order . This system is a very good thing , it keeps the inside of the engine cleaner as well as reducing exhaust emissions .
Oil splash? I don't know about others, but my engine has a sheet metal baffle under the hole where the breather installs. Is that not enough to keep oil out? Nate, I might be interested in helping clean up your backyard...
Crankcase Breathing Yes, there is still way too much oil spray flying 'round there . Look at it this way : GM first inverted the baffled Road Draft Tube and put the PCV Valve in the top of it , after a couple years of non stop Dealer complaints of high oil usage and smoking , fouled spark plugs etc. , they moved it up the hose to the intake manifold then to the Rocker Box where it belonged from the beginning . I trust the GM Engineers who made this engine for so many years . I'll keep an eye out for that factory PCV Road Draft Tube as I don't need it , last time I tried to sell it , no one was interested , I knew sooner or later this nearly impossible to find part would come in handy so I held onto it . You'd laugh if you saw the hokey-pokey home made CC Breather rig I put on my '59 Metropolitan Nash FHC ~ the BMC Series 'B' engine in it is a 1930's tech relic and I run it pretty hard so the Road Draft Tube was always spitting oil on the exhaust header , I had to do summat about that and my solution is inelegant to say the least but it works .
Hmmmm...maybe I should put mine in the valve cover. Its only a cheap-o chrome job. It won't be like I'm drilling an original
PCV Location Well ; There's a replacement oil filler cap that has a hose nipple on it , you could use that , look in the oil and radiator cap " Buyers Guide " every Partshaus has even if they don't know it or are too dang lazy to open a book , it'll have pictures.... Then re install the road draft tube so it'll have where to breathe in fresh air....
