valve cover breather

[Justins72]

Is it normal for a little smoke to come out of the valve cover breather or do I have a problem I need to find? Thanks

[MEK-Dangerfield]

I've never seen that before. Is this happening at start-up, or what?

[usraptr]

Is it smoke or vapors?  You will usually get some vapors out of it with all the pressure inside the engine.  That's why the breather is connected to the air cleaner/carb to suck them in and recycle to reduce smog. Ditto for the PCV. 

[Justins72]

It's not a lot of smoke it's probably vapor I was just expecting nothing to come out of the breathers.

[femtnmax]

With engine idling, the PCV valve should draw in ALL the crankcase vapors (all the blow by past the piston rings).  At the inlet filter for the PCV system, you should be able to place a small piece of paper over the inlet and the "draw" of the system will hold it to the breather inlet. 
If there is excess ring blow by the PCV valve will not be able to consume all the vapors, meaning that there will be excess positive pressure in the crankcase.  This will cause the piece of paper over the inlet to "fall" off. 
I would assume that if your seeing vapors you have excess crankcase pressure...first clean your pcv valve with carb cleaner sprayed in both directions.  Make sure the valve rattles freely when you shake it after cleaning.  Then clean or replace the inlet filter for the PCV system, it is located on the opposite valve cover to the one with the pcv valve on it. 
The photo shows, with the engine warmed up and idling, the piece of paper held to the inlet of the pcv system.  The system in the photo is working correctly, all crankcase vapors are being pulled into the intake manifold thru the pcv valve, there are NO vapors leaving the system..

[LAA66]

 Very interesting about the draw vs. pressure from the breather. I often wondered how the breather does not cause a lean condition, isn't straight manifold vacuum is being pulled across the engine. ?

[femtnmax]

how the breather does not cause a lean condition, isn't straight manifold vacuum is being pulled across the engine. ?

Yes, manifold vacuum is being applied to the PCV valve, but the valve limits the total flow.  The valve is spring loaded; I believe as manifold vacuum decreases the valve closes so at higher rpm there is no pcv flow.  I would assume carb jetting would have to allow for the vapors drawn in thru the valve.

[Justins72]

I don't have that type of valve cover breather so maybe that's why I'm getting a little smoke out of it

[Bullitt-]

I don't have that type of valve cover breather so maybe that's why I'm getting a little smoke out of it

Style of breather should not matter, if you have a working PCV valve negative pressure will pull air in the breather preventing smoke escape when the engine is running. I would not be surprised to see a little smoke once the engine is off.

[Justins72]

I'm pretty sure I don't have a Pcv valve and if I did I have no clue where it's at or where one would go. 

[Aussie Challenger]

Should be a PCV valve in one cover and connected to the base of the carby, the other cover as said should have a filter/breather. At idle and low engine speed any fumes from blowby will get sucked into the engine and burnt and fresh air comes into the engine through the filter/breather so there is no vac inside the mechanicals. Under hard acceleration there is more blowby and the fumes go through both the filter/breather and PCV valves. In a standard engine the breather hose goes into the air filter housing, on some performance motors some put a little filter on the rocker cover which is exposed to the air, in this setup it is not uncommon to find an oil stain on the rocker cover. Racing cars feed the breather hose into a catch can and do away with the PCV valve and feed another hose to the catch can.   

[Bullitt-]

I'm pretty sure I don't have a Pcv valve and if I did I have no clue where it's at or where one would go. 

   Well that's probably the problem...Also keeps the oil from pushing by the gaskets, standard on engines since sometime in the '50s to date, a $3.00 part.

   See item in center of valve cover with hose running to carb.




   

[CUDA JAS]

 not to hijack the post...but are they any issues with having a breather in both valve covers, as long as one valve cover has a pcv???

[femtnmax]

are they any issues with having a breather in both valve covers, as long as one valve cover has a pcv???

I would have initially said there should not be a problem,BUT....with a breather on the same valve cover as the PCV valve, air would most easily be pulled in from the adjacent breather rather than across/thru the crankcase.  Pulling air from one valve cover thru the crankcase to the other valve cover should help eliminate condensation and deposit build up.  So for street use I would say have breather on one cover only with pcv valve on other cover.  Race car would not matter.
On the older cars with "road draft tube" crankcase breather system used before pcv system, have you ever noticed how bad the carbon build up is under the valve covers and inside the engine??  It's typically real bad.  Not sure if its all from lack of pcv, but...

[72rtchallenger]

  So for street use I would say have breather on one cover only with pcv valve on other cover. 

   

not to hijack the post...but are they any issues with having a breather in both valve covers, as long as one valve cover has a pcv???

wouldn't recommend it for the same reasons stated by femtnmax