Poly Vinyl Chloride? (Just messing with you brother.
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I have seen many PCV arrangements on these trucks as well. Some of them are a bad idea in my opinion. If I were to rig mine with a PCV, I would rig it as similar as possible to a more modern inline six.
I believe that it is important to have the vacuum applied to the top of the valve cover to remove the water vapor which is known to rise to that location.
The vented valve covers on the '54 and earlier engines serve a dual purpose.
1) While underway on the open road, fumes are sucked out via the downdraft tube. This air is replaced through the vents in the valve cover.
2) While at low speeds or idle, fumes (water vapor mostly) rise to the top of the engine and are allowed to escape via the vents.
Folks have written about filling the vent holes and adding a vented cap which has filter material in it. When they removed the valve cover after driving for a significant amount of time, they discovered creamy goop on the underside of the valve cover. This would be indicative of the accumulation of water vapor which had no way to get out.
Carl
