PCV

[D35 Torpedo]

1 hour ago, kencombs said:

except that it looks just like (In flow direction/etc) to that posted by Bob R above .  And the way mine will look, if I ever get it all together.  Chev valve screwed into the manifold or carb adapter, sealed oil filler (or maybe valve covers not sure yet),   the valve cover location will avoid the flying oil in the crankcase.  And the road draft tube blocked.

I think you're over thinking it. The road draft tube is to get rid of crank case gases. The later engines had a pcv in place of the road draft. It's the perfect place for such a device.

[kencombs]

42 minutes ago, D35 Torpedo said:

I think you're over thinking it. The road draft tube is to get rid of crank case gases. The later engines had a pcv in place of the road draft. It's the perfect place for such a device.

I’ve been known to do that.   Only reason it crossed my mind is issues some had in the early PCV years, like Chevy s ‘beer can’ in the valley.   Without it lots of oil got picked up.  

[Loren]

On 5/24/2024 at 11:03 AM, kencombs said:

You are correct regarding backfire protection. But, the description of flow direction does not match my understanding.   All PCV systems introduce the crankcase vapors into the intake path, after the air filter.   If the oil fill is sealed and a hose attached from that tube to the air cleaner, the purpose is to filter the air entering the crankcase.   The vacuum from the PCV valve pulls the fumes from the crankcase.  

 

air cleaner to crankcase to pcv valve to intake manifold, is the flow ain my inderstanding.

 

That is what I was taught and believed for the last 60+ years of dealing with them.

In an earlier post on this I mentioned that the amount of blow by past the piston rings can exceed how much the vacuum can draw out of the crankcase. It has to go somewhere and that somewhere is either the breather cap on the oil filler or in the second type it goes to the air cleaner and gets sent into the intake stream.

Thus while the vacuum side is all one way, the breather side can be two way. That is why the closed system is the only type now allowed under emissions regulations.