On 140's, the 3/8" hose that leads from the oil trap on the side of the block to a T between the vacuum boost for the brakes and the manifold usually has a silver one way valve that "rattles". I'm assuming it's designed to allow oil vapor through from the crank case, but won't allow back pressure to go back into the crank case.

Is this valve required? Can they still be found?

I went to a few parts stores last night looking for some of the suggestions posted here. The Napa part number was no longer in their system. The chevy PCV valve was in there, but unavailable. The Porsche one listed on a link probably needs to be had at a dealership.

They did have a PCV valve "section" with about 75 different models. I picked through all of them and bought one with a design the closest I could find to what I remember was on my B18. An inline can style with a rattling valve. They all seemed very similar in function to me, with only the differences in the weights of the valves being the changing factor. I tried to pick the lightest one I could.

This seems to be the best I can do at this time, so I'm going to give it a try.

Hi,


Be aware that removal of fhe flame arrestor could result in the detonation of crankcase fumes, which could easily force all oil seals from their housings.

http://members.rennlist.com/pbanders/pcv.htm


Goatman

It's tough to find a new PCV suitable for four cylinder engines. It's best to install the restricted orifice in the manifold to vent the crankcase gases at idle. It won't work the power brake booster though.
For sure you must not allow unrestricted manifold vacuum to pull on the crankcase. The carbs won't like it...

Agreed, but I'm using vacuum at the air filter, before the jet and butterflies, so I didn't think I'd affect the mixture at all...

An AC CV584C was mentioned here on BB as being correct. Actually for Chev 6cyl 67-72. One on eBay at the moment for $30 but I've seen them a LOT cheaper.

I think the fully sealed oil filler caps are from the B21/23. They do look the same.

If the PCV valve is the same as the one used on the 122's, then use
a NAPA CRB29213 or equivalent. Price a year ago was about $7.00.

I'll see if I can find that valve, thanks.

It didn't occur to me that the cap I found was from a 240, I do remember now that they do look the same.

Do you think it's a bad idea to run a sealed cap, if I'm venting from the crankcase?

The "rattle" valve is called a PCV valve.
Like George said, B18 equipped cars had them.
They are still available, but are not one-size-fits-all.
The ones on B18 cars have two different size nipples.

Required? You can get away without it.

What year is yours? They changed early in the run of the 140s.
Later ones had a fitting with a small orifice and no "rattle" valve.

I'm actually running a '74 B20 converted to SU's. Not sure what was on there when it had D-Jet, but it's been venting to atmosphere since the conversion.

The PCV system has a lot of different configurations. I currently have a filler cap with hose barb and hose running to the forward carb. On the tear drop side there's a small filter and just open to atmosphere. My understanding was that keeping one side of the system at a vacuum allows for positive flow through the crank case, removing contamanents.

However, I have no restriction of flow in my setup. Therefore, air can flow through the crankcase as fast as the vacuum of the carb can pull it. I've also been struggling with the filter on the tear drop oil trap getting pretty gummed up with oil residue.

I was hoping to reverse the PCV plumbing. I obtained a filler cap with no hose barb, and also doesn't appear to be vented at all. Did they make those caps that were completely sealed? If I had one that was completely sealed, that would certainly restrict the flow through the crankcase.

I found this comment from a past brickboard post:

Whichever way you hook it up, you need a restriction in the flow path. That can be a PCV valve (the B18 way) or a metered orifice (the B20 way) -- which is fitting with a small hole in it attached to the manifold, not an open fitting.

My real question right now is, what kind of restriction do I need? Could a sealed filler cap do it? Did I do any harm to my engine by encouraging such a high rate of flow through the crankcase?

I'm confused.
If you use a sealed cap, where will you get the clean filtered air that is supposed to enter the crankcase?

Although you do want some vacuum in the crankcase, you do not want it at the same level as the intake manifold.

It sounds like you are attempting to seal off the crankcase with the exception of the vacuum. That is not what you want to do. If you think that oil breather filter is getting clogged quickly with minimal vacuum, wait until you are applying 15 inches!

I think you're right, although my original thought was that if I kept the crankcase at vacuum, I'd only pull out those contaminants that outgassed like boiling water, etc. Stuff that was a condensed liquid when cold.