Is it really necessary?

[Ghoste]

Yes, that''s true, but if you put your thumb over the hole in the valve cover where the pcv plugs in, you'll feel outward pressure.  (we're getting into semantics I think, whether it sucks or blows, the end result is the same)

[Headrope]

That's exactly why I started this thread: I had the PCV hose off and felt the outward pressure at the valve. The outward pressure seemed to me to be an indication that the crankcase vents itself, so I thought I'd ask.

Ultimately I think the additional vaccum created by the carb may be beneficial, but not necessary as a means of evacuating the crankcase; it's supplemental. By removing the PCV and going with dual breathers I could accomplish the same thing and take advantage of whatever gains in power might be the result of having only air and fuel in the cylinders.

Please feel free to continue the debate. I think the question has been answered.

Thanks everyone for your help.

[my73charger]

Sorry to revive such an old topic, but I am getting rid of my PCV and going to dual breathers.  Ron, is this one sufficient?

[TylerCharger69]

If I may add....I'm not too sure about stock valve covers, but I know that most aftermarket pieces have sheet metal baffles that can be mounted inside of the valve cover to help prevent oil from making a mess.  But it seems to me, that somewhere between the valve cover and the carb should be a filter to keep oil from being sucked into the carb itself which is why a lot of people just use pcv filters on the cover instead of the pcv valve to the carb

[elacruze]

Crankcase pressure has an significant effect on engines-but only at high RPMs. A couple reasons;

There is always some amount of energy wasted by the pistons pushing crankcase air around. In fact, your 2-cycle dirt bike operates using crankcase pressure to move the fuel/air charge into the cylinder. So in a 4-cycle engine, making this movement easier or operating at lower pressure translates directly to horsepower. Crankcase volume to displacement ratio is one metric for figuring pumping losses.

Additionally, at high RPM oil tends to stick to the crankshaft in a wind vortex. Eliminate or reduce the amount of air in the crankcase, reduce crank windage and oil aeration.

The Pro-Mod guys with enormous engine displacement use crankcase pumps which are large and use a lot of power to operate. Why?

As far as oil in the combustion chambers, it's never a 'good' thing, but cruising around town the amount that passes through a PCV system is insignificant. If you were going to the track, you'd want to disconnect it and get some more adequate vacuum producing system in place. Rule of thumb is the longer your stroke, the higher your RPM, the more you need crankcase vacuum. Oil reduces the Octane of gasoline, so any time you're near detonation it can be the straw that breaks the camel's back. Oil also produces ash which coats your nice smooth combustion chambers, valves, and ports.

Lastly, how many of us have any idea how good our ring seal is? How many of us know how much oil gets up through the cylinder? Through the intake valve seal? The PCV isn't the major culprit in unfresh engines.

Ultimately a PCV system is good for the environment and keeps oil off your headers, but it does not have the capacity for evacuating effectively during anything more than casual street driving. Personally, I'll incorporate a PCV system in my touring version next summer though it will be of higher capacity than stock. 

[Purple440]

Thanks for bumping this one elacruze, I hadn't seen it.  I was recently thinking that my PVC hose was just bringing in hot dirty air into my carb and am thinking of capping it and putting an air cleaner on like I have on my passenger side. 

Any reason not to?

- Doug

[elacruze]

Thanks for bumping this one elacruze, I hadn't seen it.  I was recently thinking that my PVC hose was just bringing in hot dirty air into my carb and am thinking of capping it and putting an air cleaner on like I have on my passenger side. 

Any reason not to?

- Doug

Well...no.

Any argument in favor of a PCV setup is largely academic, the benefit being pretty much limited to environmental concerns.
Valve cover breathers and a premium windage tray are best for power, PCV for high-vacuum cruising.
I'd have breathers on both valve covers. Not so much a problem anymore, but in the pre-synthetic oil days, paraffin base stock oils were famous for leaving a thick coating of nastiness inside the valve covers due to the relatively cool covers condensing the mist. Breathers help that mist make it out of the engine.

[firefighter3931]

Any argument in favor of a PCV setup is largely academic, the benefit being pretty much limited to environmental concerns.

My thoughts exactly 

Valve cover breathers and a premium windage tray are best for power, PCV for high-vacuum cruising.
I'd have breathers on both valve covers. 

Yep 


Dang....this is an old thread, LOL ! 



Ron

[firefighter3931]

Sorry to revive such an old topic, but I am getting rid of my PCV and going to dual breathers.  Ron, is this one sufficient?

Yep that will work but personally I prefer the taller stack style breathers which allow for drainback. The lower style breathers are vented underneath and will oil mist your engine under hard acceleration. 

Here's what i have on the Black Pig.



Ron

[my73charger]

Thanks guys!   

[1974dodgecharger]

wow, old thread, but im assuming RON you still run both breathers still?

I did a search on breathers becasue I have mine plumbed under the air intake system and now reading further oil gets pushed through the pcv now I dont want it in my air pan now gheeez.

I think im gonna get me another air breather for the other side.....

[jlatessa]

Here's something to consider, I purchased a Steeda Oil Separator Kit from a Mustang supplier,
it operates the same way an air compressor oiler works, but in reverse.

You plumb it in between your PCV valve and the intake manifold and it precipitates the oil vapor
and collects it in a clear plastic bowl that has a push valve at the bottom for emptying.

They sell two sizes, (I bought the small one) but haven't installed it yet.
It seemed to me a good solution to fume evacuation and yet not screwing up your
combustion process.

Joe

[myk]

Here's something to consider, I purchased a Steeda Oil Separator Kit from a Mustang supplier,
it operates the same way an air compressor oiler works, but in reverse.

You plumb it in between your PCV valve and the intake manifold and it precipitates the oil vapor
and collects it in a clear plastic bowl that has a push valve at the bottom for emptying.

They sell two sizes, (I bought the small one) but haven't installed it yet.
It seemed to me a good solution to fume evacuation and yet not screwing up your
combustion process.

Joe

Pricey bastards, aren't they?

http://www.latemodelrestoration.com/item/ST-5553710/1979-04-Mustang-Oil-Seperator-Kit?utm_source=google-shopping&utm_medium=comparison-shopping&utm_campaign=google-shopping-v2&year=2000&gclid=CImhv_PmwrwCFYqPfgodGDEArA

[jlatessa]

I'll say...no bargains anywhere these days, but it looks well made.
I plan on using it for street driving and using the header collector
evac system for the track.

Joe

[myk]

I'll say...no bargains anywhere these days, but it looks well made.
I plan on using it for street driving and using the header collector
evac system for the track.

Joe

Oh the system definitely has its worth, for sure.  I think I remember on an 'LS1 forum they had home-made ones going on...

[firefighter3931]

wow, old thread, but im assuming RON you still run both breathers still?

Yep, same valvecovers and breathers that were on the old 446 are now on the 572....still working fine. 



Ron

[Mebsuta]

Ultimately a PCV system is good for the environment and keeps oil off your headers, but it does not have the capacity for evacuating effectively during anything more than casual street driving. Personally, I'll incorporate a PCV system in my touring version next summer though it will be of higher capacity than stock. 

I agree.  PCV is closed and not even working at WOT when there is no manifold vacuum, unless you are using fixed orifice valve.  I use it because I am a casual street driver. 

[1974dodgecharger]

As cooter would say I have a hard time believing you guys are casual drivers.  You guys never nail it when your out?  Never mash the peddle at all?  I mash my peddle even on the highway downshift to 3rd and go away to get away from folks who cant drive. 

Even if you do casual driving why even have the PCV anyways when its only for the environment only?  If one cared about the environment then theres the honda civics out there that get great gas mileage.

[Mebsuta]

As cooter would say I have a hard time believing you guys are casual drivers.  You guys never nail it when your out?  Never mash the peddle at all?  I mash my peddle even on the highway downshift to 3rd and go away to get away from folks who cant drive. 

Even if you do casual driving why even have the PCV anyways when its only for the environment only?  If one cared about the environment then theres the honda civics out there that get great gas mileage.

Casual meaning I don't know how much hp my old RR makes on a dyno, don't know what the 1/4 mile ET is, and don't care.  I will mash it when the coast is clear, but I'm not a street racer either and I don't cruise the burger stand.     

[1974dodgecharger]

but you do mash it so PCV is for?

Im curious now why have the PCV if its just for environment and it is only operarting at near idle and light cruises.

endless debate I guess....Ill stop there. 

As cooter would say I have a hard time believing you guys are casual drivers.  You guys never nail it when your out?  Never mash the peddle at all?  I mash my peddle even on the highway downshift to 3rd and go away to get away from folks who cant drive. 

Even if you do casual driving why even have the PCV anyways when its only for the environment only?  If one cared about the environment then theres the honda civics out there that get great gas mileage.

Casual meaning I don't know how much hp my old RR makes on a dyno, don't know what the 1/4 mile ET is, and don't care.  I will mash it when the coast is clear, but I'm not a street racer either and I don't cruise the burger stand.     

[Mebsuta]

If you get in your car and run some errands and go places, you will spend a lot of your time idling or at part throttle.

I can't drive to the post office or Walmart with the accelerator flat on the floor the whole time.