Too much PCV?

[DeeVeeEight]

I have gotten my 383 running again after a bit of a scare. Now I have an intermittent smoke issue. Here's the scenario... No smoke on start up. No smoke on acceleration. No noticeable smoke while cruising but that is hard to tell with tinted windows and mirrors...
I do get smoke occasionally when the motor is hot and at idle. I was originally thinking a worn valve seal but that would give me some smoke on start up and possibly a fouled plug and/or misfire. Then I got to thinking maybe too much suction at the PCV valve so I pulled it out of the valve cover. The PCV valve was buzzing like a bee and had a lot of suction, it is plumbed directly into the base of my single plane intake manifold just under the carburetor. Is there a way to decrease the amount of vacuum there so I do not pull oil out of the motor and into the intake?

 

[mrvette]

U maybe remember my 355 roller engine has had about every configuration and some stupid operational issues, including a bad ROLLER cam, but aside from the other issues, there was the issue of the PCV valve in the valve cover, no matter what internal baffle was there, and I had aluminum cast covers, olde tyme stamped steel covers, and now with the L98 heads I have the cheep steel covers with 4 down the top.....

in all cases, if the PCV valve was in the cover, either side, the engine used oil....never enough to smoke, essentially same symptoms as you have, I used to have a L98 injection on it, valve in cover.....I finally got smart and put a highly modified LT1 induction, it was done in frustration looking to simplify the induction as part of that damn CAM troubshooting....BUT the LT1 induction has the PCV valve in the side of the unit, obviously looking down into the cam space.....with a metal plate to keep oil splash in line....

THAT is what cured the oil consumption problem, I knew it was PCV related because of the oil in the vacuum hose.....but then being an old Poncho lover from decades ago, I remembered the valve was located in the pan cover, and I NEVER had an issue.....so now I have two fake/gutted valves in the covers, one is open to air, the other goes to the PORTED vac on the throttle body, along with the fuel evap canister....


:crylol:

 

[DeeVeeEight]

Looking at what I had in place, it seems my PCV system was somewhat redundant. In addition to the PCV valve I have a breather/vacuum hose that comes off of one valve cover and is plumbed in to the base of the air cleaner. Basically I had two sources of vacuum venting my crank case. I eliminated the PCV valve and installed a new rubber grommet in the valve cover that accepts a nice chrome filtered breather cap on the one side (air in) and kept the breather/vacuum cap on the other valve cover (air out). So now I have an open system instead of a high vacuum PCV valve. Hopefully the reduced vacuum will stop the smoke and oil consumption issue.



I had this plumbed in to the air cleaner PLUS a PCV valve. I eliminated the PCV valve and installed a breather cap on the opposite side.

 

[MYBAD79]

So the other valve cover had a pcv valve and hose plumbed to the intake manifold?
Where did you get air into the engine?

It should be a lot happier the way it is now, although I would plug the bottom of the air cleaner and run the pcv hose to the manifold instead, either way should be fine though.....

Unrelated story: my air cooled VW engine is designed to pull air thru the front crank seal - I've read that if you add a breather to pull air in, it will leak oil out the front seal..... Seems to be a very popular mistake on these engines....

 

[DeeVeeEight]

So the other valve cover had a pcv valve and hose plumbed to the intake manifold?
Where did you get air into the engine?

It should be a lot happier the way it is now, although I would plug the bottom of the air cleaner and run the pcv hose to the manifold instead, either way should be fine though.....

Unrelated story: my air cooled VW engine is designed to pull air thru the front crank seal - I've read that if you add a breather to pull air in, it will leak oil out the front seal..... Seems to be a very popular mistake on these engines....

It was pulling air in from the passenger side valve cover (through the air cleaner) and out the driver side through the PCV valve. Now it is flowing in the opposite direction.

Negative pressure on the engine seal.... It would be nice if the rear main seal on my Buick had negative pressure. It likes to mark it's territory.

 

[MYBAD79]

You were not pulling air in from the air cleaner, there's low pressure in the air cleaner, it actually sucks air from the valve cover, not the other way around.

What has worked best for me is: vacuum port on manifold connected to valve cover (pcv valve plug in style) ...the other valve cover just has a breather open to atmosphere

 

[BangkokDean]

You were not pulling air in from the air cleaner, there's low pressure in the air cleaner, it actually sucks air from the valve cover, not the other way around.

What has worked best for me is: vacuum port on manifold connected to valve cover (pcv valve plug in style) ...the other valve cover just has a breather open to atmosphere

That is what I do also....

 

[DeeVeeEight]

]You were not pulling air in from the air cleaner, there's low pressure in the air cleaner, it actually sucks air from the valve cover, not the other way around.[/COLOR]

What has worked best for me is: vacuum port on manifold connected to valve cover (pcv valve plug in style) ...the other valve cover just has a breather open to atmosphere

I am pretty sure that the increased vacuum from the PCV side was overpowering the low pressure area in the air cleaner. That being said, having two vacuum sides and no air inlet was sure to cause an issue. I am trying to pass a smog test. I hope that disconnecting the PCV valve with it's blow by gases and eliminating it as a possible source of vacuum leak will allow me to get the emissions in line.

 

[mrvette]

]You were not pulling air in from the air cleaner, there's low pressure in the air cleaner, it actually sucks air from the valve cover, not the other way around.[/COLOR]

What has worked best for me is: vacuum port on manifold connected to valve cover (pcv valve plug in style) ...the other valve cover just has a breather open to atmosphere

I am pretty sure that the increased vacuum from the PCV side was overpowering the low pressure area in the air cleaner. That being said, having two vacuum sides and no air inlet was sure to cause an issue. I am trying to pass a smog test. I hope that disconnecting the PCV valve with it's blow by gases and eliminating it as a possible source of vacuum leak will allow me to get the emissions in line.

Just a thought, maybe insert a flew re stricter in to the line?? cutting down the internal diameter?? thereby keeping the appearance for the inspectors???

:amused:

 

[DeeVeeEight]

I thought about that Gene, maybe some smaller diameter vacuum hose inside the larger one.