pcv question

[69heavychevy]

Hi everybody. the other day i got the bright idea to get rid of my pcv and put a breather cap in its place. on the carb were the pcv hose was connected i put a little tuner breather/paper filter. now the truck seems to idle really high obvouisely, you can really hear the carb sucking in all that extra air. it almost sounds like i have a blower. anyways my question is wether theres any advantages to running a setup like this. the motor should still be getting vented properly through the cap breather on the valve cover right. one thing i noticed is that my truck is a little harder to start, i have to give it some gas so it wont stall.

[GREASEMONKEY72]

if youre having to give it gas so it wont stall its because the hole where the hose went to under the carb isnt sealed good enough, but it should be fine cause my pvc is there but not working, i stuffed it full of silicone and my truck runs fine

[GREASEMONKEY72]

i just noticed that you said you put a breather on the carb where the hose went and thats why it wants to stall, you need to go to the parts store and get a little cap to put over it then it wont stall

[brak]

You have to seal off the PCV port on your carb/throttle body. essentially you have a huge vaccum leak leaving it open, and that's the sound you are hearing, all the air being sucked through the little filter you installed.

Get a cap from your local parts store.

[cdowns]

dumb idea

[WorkinLonghorn]

Don't be surprised when you start getting a miss,and discover a burnt piston.You are running WAY lean like that.
There is a very good and sound mechanical justification for the PCV system and it should be installed and working properly. What is gained by disabling it anyway?

[dave2953]

I agree with working Longhorn. With that breather attached to the carb base, you are sucking additional fresh air into the motor; it's acting like an extra air cleaner which will affect your fuel air mixture. I also don't think the breather you have installed on the opposite valve cover will extract hydrocarbons as efficiently as a PCV system. They've been in use for 40+ years for a reason, but it's your truck.

[kwmech]

If I was disabling all the smog systems on my truck, that would be the one thing I left alone. It removes the hydrocarbons from the unburnt fuel that finds its way into the crankcase and also removes moisture thus helping to keep the oil clean

[Texasdeere]

Originally Posted by kwmech

If I was disabling all the smog systems on my truck, that would be the one thing I left alone. It removes the hydrocarbons from the unburnt fuel that finds its way into the crankcase and also removes moisture thus helping to keep the oil clean

Just leave the pcv hooked up, I can't see how it would hurt the engine or performance in any way. Plus it is not big enough to be an eye sore.

[69heavychevy]

thanks for all your input, i guess its going back on.

[bobthecop]

Great idea, I had a 350 w[o a working pcv and it ran like crap and I had v/c seals leaking and lots of oil blowing thru the breather on my valve covers. Put a working pcv in problem solved.

[70rs/ss]

They came up with the PCV (positive crackcase ventilation) because cars caught on fire and some blew up. The fumes (blowby) need to go somewhere and back into the combustion chamber is the best and safest, it can marginally help mpg, but will keep you from having a big fire ball erupt under your hood!! You need a breather on one valve cover and the pcv on the other. I had a front seal make a weird noise once when I had suck on one side and no inlet on the other!! I was baffled by that one!!

[68speedalert]

Originally Posted by cdowns

dumb idea

Makes no sense to get rid of it on a street driver.

[GREASEMONKEY72]

after reading about the sludge and mpg and the others i think ill put mine back on becuase id never heard any of that before all i heard was that it was just a breather and figured why bother with if its just a breather but thanks for the new outlook on it and ill go get a new one and put it in this weekend

[piecesparts]

Plug the big vacuum leak, on the carb.......

Can you give us an idea of why you put a filter on the carb's PCV connection port?

[hvychve]

The P.C.V system is not a power robbing component, (positive crankcase ventilation) It's purpose is to remove crankcase pressures built up in the crankcase from blowby gases that produce during combustion. by removing this and just venting to atmospher is ok, but , why just be ok, why not be better and have the engine just pull em out and reburn? As far as your high Idle, I will agree with above mentioned, you have to PLUG it off completely, not filtered. but in my opinion, I would want the pcv on and working.

[RedZ71]

yeah my pcv lines are not hooked up, and mine idles REALLY high when its out of gear. i wonder if thats why it idles so high?

[WorkinLonghorn]

Yeah that's probably why. Hook it back up! You will damage your engine running so lean.

[muddpile]

The stock PCV things are a complex looking little unit with moving parts in them and such, where the aftermarket ones are just an empty tin can with a hose barb on one end (like a breather with no guts in it and a hose barb out the side). Is there any advantage/disadvantage to either style?

Also, on the other valve cover, is it better to run an open element breather, or a pipe to the air cleaner? Thanks!

[rage'nrat638]

guy's you half to have a pvc valve.. it's like a truck with no brakes

[piecesparts]

Originally Posted by muddpile

The stock PCV things are a complex looking little unit with moving parts in them and such, where the aftermarket ones are just an empty tin can with a hose barb on one end (like a breather with no guts in it and a hose barb out the side). Is there any advantage/disadvantage to either style?

Also, on the other valve cover, is it better to run an open element breather, or a pipe to the air cleaner? Thanks!

I want to scream foul here. The stock PCV is a PCV and always will be PCV. The other thing that you are talking about is the breather inlet from the air cleaner connection, that is why it is empty "tin can" and has a connection on it for a hose. That is the shiney way of connecting that valve cover to the air cleaner, so that you can get fresh air to the engine, without having a nasty stupid looking plastic POS out there where it looks like a stock engine.

I stand by that one should always have the PCV valve in the flowpath--it does a couple of things: 1) provides a back flow check valve in case your engine backfires and, 2) it gives a restriction (throttled orifice) for the vacuum flow from the engine crankcase--so you won't have that fast idle condition. It is a designed vacuum leak, not a gaping hole in your intake manifold. That way you control the leak and do not run lean.


If you so choose, you can run the engine, as they did in the old days with just a breather or two on the crankcase. I don't recommend it, because the design of the PCV system maintains a slight vacuum on the crankcase, thus eliminating all of those unsightly oil leaks and making the engibne work less.

[GREASEMONKEY72]

i dont know about the high idle thing becuase mine idled the same before and after i plugged up the pcv, the idle screw needs to be turned down to lower the idle

so is there a real advantage to running a pvc vs not running one?

the reason im thinking of putting it back is becuase i saw something about better mpg other than that i have 2 breathers, and about the backfiring, my truck backfired a couple times before i plugged it but since i plugged it up it hasnt backfired, i dont know im just confused, like usual

[dave2953]

Your truck most likely backfired as a result of hydrocarbons igniting. As mentioned earlier in the thread, the PCV rids the crankcase of these flammable gases, which are a byproduct of combustion. You're lucky you didn't have a catastrophe. The PCV also helps to prevent sludge from building up in the motor. This system would not be omnipresent in the automotive world if it didn't serve a purpose. I would put it back if I were you, but that's just my opinion.

[68speedalert]

Originally Posted by GREASEMONKEY72

i dont know about the high idle thing becuase mine idled the same before and after i plugged up the pcv, .....

With the engine running, check for vacuum at the pcv valve. (Pull the valve from the valve cover and put your thumb on the bottom of the pcv). There should be. If not, you have it hooked to the wrong port on the carb.

As to the question as to if you should run it......

The board members who are telling you to run it are either mechanics, have been mechanics, or know a lot about engines. I've seen some of their posts in the past , for what it's worth, they know their sh*t.

You decide who is right......I already do.

[jacobs]

The military started using pcv back in the 1940's on their vehicles....long before anyone even thought of emission controls. There is a reason for them.