PCV experiment with low vacuum

Buzzman, see above. We crossed in the ether it seems! Basically a PCV valve has a range of operation, with zero flow at one end and a small metered flow at the other. The middle is full flow.

Chris

Have you considered installing an oil catch can on the pcv hose to see if the pcv system is sucking to much oil?

Edited by FSJunkie - Apr/22/2018 at 2:48am

Update! It looks like we may be on the right track. I just pulled a plug to see if there was any difference after 20-30 miles. It has gone from being a dark brownish black colour to a nice light tan-grey. Before the change they looked like a brown colour with a light coating of black over them.

I have not so much as touched a mixture or idle screw, so I can only attribute it to the PCV change. Let me see what happens to the oil consumption next.

Thanks!

Chris

The "poppet" in the center of the valve has angled sides, basically it's a cone. The cone goes further into an opening on the end with high vacuum, so flow is decreased the further it goes into that opening, but it will only go so far. I was thinking it would be more at high vacuum, but once you look at a cross section of the valve the idea that it will flow less than expected at high vacuum (and more flow in the middle of the vacuum range) makes sense. Of course at very low/no vacuum the spring keeps the poppet seated (closed off) on the other end, and a backfire through the PCV tube would force it closed.

Speaking of a PCV tube/orifice instead of a PCV valve... Most modern cars, including the 4.0L AMc/Jeep engine, use just an orifice tube. There is a baffle inside the 4.0L valve cover. I suppose it's made in such a way as to prevent a backfire from entering the valve cover, but it's been a long time since I had one apart. I do remember taking mine apart and cleaning when I changed to a newer head, but that was 6-7 years ago. I don't remember any kind of valve or flapper, but it may be there...