PCV vs. Breather.....

[Slammed70]

Well I found where that burning oil smell was coming from, one of my breathers is leaking from under where the vents are. And my "old know-it-all" neighor told me I should ditch one of my breathers(I have one on each valve cover)and sustitute a PCV instead.

Just wondering what that would do for me?

[clay68c10]

It lets the engine suck in that excess crankcase pressure so it doesn't build up and cause your current leak.

[Slammed70]

Oh, so they are a good thing then....

Aight, Ill pick on up tomorrow.

[1970 chev truck]

i dunno i have two breathers on one side and i have no leaks at all

[Longhorn Man]

there is absolutly no good reason to NOT have a PCV system. Yes, it is a smog control item, but it costs no power, and is a great benifit to your engine.

[Sinisterspeed]

yeah, What he said. I have one on my engine. It doesnt need it to operate so when the neighbor kid was installing his engine that seemed to have excessive blow by or high block pressure in his ..... FORD... I robbed my brand new grommet,PCV and hose. Put it on his valve cover and poof no more blowing the dipstick out of his engine. Needless to say he has yet to replace the parts but Mine ran fine without issue for its long trip outside the other day. I will still replace it and always have one on my engine as well.

[Slammed70]

I was gonna get one, but it slipped muy mind when I was handing the parts store guy all my money. And the closest parts store is ~30 miles away so it wasnt in my plan to turn around and buy a $4 item if I didnt need one, since I have a bucket full of breathers Ive pulled of my other engines. So I just threw them on as a temporary fix so I can get it going, and forgot all about it until now.

[dwcsr]

The PVC does serve a purpose. It draws out the gas fumes from the crank case when you flood or the rings don't seal like they used to and the gas passes the rings. One good back fire with fumes in the pan and it will come off promptly, I'm sure you've heard of grenading the pan.

The other purpose is to help seal the rings when running. Vacuum in the crank case is a good thing it actually add HP.

[Longhorn Man]

plus the natural bybrouct of combustion hangs out in there as a very corosive gas and becomes acidic. It then contaminates the oil and atacks the metals inside the engine.

[68_chop_top]

The breather allows air into the valve train and crankcase. The PCV draws air OUT from the block and is routed to under the carb where the gases are burned in combustion. You need both.

[jonnybravo]

i have pretty severe blowby is it ok to put another pcv valve on the other too and then tee the two together

[Longhorn Man]

Originally Posted by 68_chop_top

The breather allows air into the valve train and crankcase. The PCV draws air OUT from the block and is routed to under the carb where the gases are burned in combustion. You need both.

I guess I should have clerified and described/explained the whole system again when I said it is benificial to install. The needing both was implied. A PCV with no breather/air filter tube will do nothing except probably suck the intake and/or valve cover gaskets into the engine.

cparman, let your buddies raz you all they want. You have the correct set up.
jonnybravo, the only way you can do this and have it work properly, would be 2 PCV valves on one valve cover, and breather/tube to air cleaner on the other. If you just go valve on one side, and valve on the other side with no way to get air in, you will suck the gaskets into the engine.

[jkeating1]

Originally Posted by Longhorn Man

I guess I should have clerified and described/explained the whole system again when I said it is benificial to install. The needing both was implied. A PCV with no breather/air filter tube will do nothing except probably suck the intake and/or valve cover gaskets into the engine.

cparman, let your buddies raz you all they want. You have the correct set up.
jonnybravo, the only way you can do this and have it work properly, would be 2 PCV valves on one valve cover, and breather/tube to air cleaner on the other. If you just go valve on one side, and valve on the other side with no way to get air in, you will suck the gaskets into the engine.

When I read this, I chuckled thinking you were kidding about sucking the gaskets into the engine. Then I remembered that, when I was replacing the VC gaskets on mine, the long, straight sections of the gasket between the bolts was drooping on the top, and not seated along the bottom. I never put two and two together, but I did replace the oil fill cap because it was caked with oily, greasy, dirt and likely not venting at all. Thinking back, I guess it was trying to suck the VC gaskets into the engine!

[68_chop_top]

The more the better! Better to burn the gases rather than blow off to the environment.

[cparman]

I have a PCV in the right valve cover, and I plumbed a tube from inside of the air cleaner to a grommet in the left valve cover. This way you have clean ( well cleaner ) air going into your motor. My buds think I think too hard, but the air going into the engine is filtered. If someone on the board will talk to me like I am stupid, and explain the picture thing I will post a pic of this, and my truck

[leddzepp]

If for no other reason, you should run PCV to keep oil from blowing all over your engine compartment. It keeps it a whole lot cleaner.

[mvfd70]

What about those of us running a 6 cyl. What would be a correct set up for engines with only one valve cover?

[Longhorn Man]

Originally Posted by mvfd70

What about those of us running a 6 cyl. What would be a correct set up for engines with only one valve cover?

The same way they did stock. A PCV in one hole, and a breather/clean air tube from the air filter.
You can't see it too well in this photo, but you can see the breather tube on the drivers side of the valve cover going to the air cleaner. I'll assume the PCV is under the air foter towards the rear.

[72-c20]

Originally Posted by leddzepp

If for no other reason, you should run PCV to keep oil from blowing all over your engine compartment. It keeps it a whole lot cleaner.

yeah..... I swapped carbs 2 days ago and left the PCV valve not connected to a vac source.... bad juju. the breather tube was puking oil all over!!!

redid the connections with all hooked up and it's much happier (and cleaner)

[heathbirkendahl]

How do you tell when the PCV is bad? And it move around and still be bad? Mine moved but did not rattle. Made more a thunking noise.

[truckster]

The PCV valve should rattle when you shake it. You can usually clean them out with a little brake parts cleaner if they're not too dirty, but they're also really cheap, so it makes sense to replace it.

[heathbirkendahl]

Originally Posted by truckster

The PCV valve should rattle when you shake it. You can usually clean them out with a little brake parts cleaner if they're not too dirty, but they're also really cheap, so it makes sense to replace it.

Ok. Mine did NOT even come close to rattling. It was clunky and has an oily film in it.

[fastcam1]

what about the old small blocks 67 and earlier like the 327, you had the oil fill tube in front with a breather on it where was the PCV?

[jaros44sr]

Originally Posted by fastcam1

what about the old small blocks 67 and earlier like the 327, you had the oil fill tube in front with a breather on it where was the PCV?

They had a road draft system which was evacuated to atmosphere. Basically, the external tube was cut at an angle, as you drove the air rushing past caused a vacuum pulling gases out of the crankcase. There was a baffle in the lifter valley

[fastcam1]

So I have a set of Chevy script valve covers, what do I have to do so I don't have to drill holes in them?
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