why would someone remove the PCV valve?

[Lance-ftw]

topic says it all really...

I bought my truck a few weeks ago and took it up to the shop I've been using for my fiance's car and my old kia before it went boom. They did a bunch of random work like seals, gaskets, etc, and while inspecting things noticed I had no PCV valve, the grommet in the valve cover had some wadding packed in it and tape

They put one in for me but it's bugging the heck out of me, why the hell would some one remove that? What benefit does it present?

i've been watching my oil pressure carefully since then because in my head I keep thinking there had to be some reason they pulled it in the first place, maybe the engine ran on low pressure with one in but in that case wouldn't you just get a stronger valve? I dunno... I'm confused... show me the light smart people!

[Longhorn Man]

the PCV won't do anything to help nor hurt oil pressure.
People remove it becouse they don't understand it. Yes, it is a smog control piece, however, it also makes the oil, and engine last longer.
At least once a year i end up explaining how it works, and why you need it on here.

[Lance-ftw]

Originally Posted by Longhorn Man

the PCV won't do anything to help nor hurt oil pressure.
People remove it becouse they don't understand it. Yes, it is a smog control piece, however, it also makes the oil, and engine last longer.
At least once a year i end up explaining how it works, and why you need it on here.

Well thanks. Guess I'll do a little more research. I'm still learning the engines various little bits.

[GRX]

Can you say sludge monster?

PCV = Positive Crankcase Ventilation. Basically it replaced the draft tube. The system utilizes intake vacuum to suck the compression stroke blow-by gases out of the crankcase; thus minimizing excessive carbon build-up in the oiling system.

[Lance-ftw]

Originally Posted by GRX

Can you say sludge monster?

PCV = Positive Crankcase Ventilation. Basically it replaced the draft tube. The system utilizes intake vacuum to suck the compression stroke blow-by gases out of the crankcase; thus minimizing excessive carbon build-up in the oiling system.

on the flip side though doesn't it end up getting gunk elsewhere because of where it's hooked up? I imagine some oil mist makes it back up into where it gets its vacuum.

[ChevLoRay]

Before '62, we didn't have any PCV valves. Then, Californias' CARB (or whatever they called it back then) decided that the smog that was present would be better controlled by doing away with the road draft tube and replacing it with the PCV valve, a valve designed to allow the crankcase oil fumes to be sucked into the intake, or the air cleaner, depending on the PCV system and the engineering of the day.

They went so far as to mandate that vehicles as old as 1955 had to have one and the road draft tube had to be blocked off. So, you may find a plug where the tube was attached....on the back of the block....near the distributor of a small block. That is where the early PCV valves were installed.

Back then, we didn't like someone changing the way things were, so some people would put a draft tube back on an engine, if they could. It wasn't until later in the 60's, that the crankcase fumes were pulled from the valve cover. Then, they found that the valve covers needed baffles and added them.

PCV valves suck...or they're supposed to.

[Lemield]

Willys Jeeps have had a PCV valve since they started building them. My 1949 CJ2a has one.

[GRX]

Originally Posted by Lance-ftw

on the flip side though doesn't it end up getting gunk elsewhere because of where it's hooked up? I imagine some oil mist makes it back up into where it gets its vacuum.

Yes. As you'd imagine, the problem gets worse as blow-by gasses increase with cylinder wear. How many of us have removed the PCV valve from an older running engine only to be treated to a nice big puff of smoke? Additionally, the one way valve is supposed to arrest any flame front (back fire) from reaching the crank case. Ever seen someone blow their valve cover? Baffles have a dual purpose.

Originally Posted by Lemield

Willys Jeeps have had a PCV valve since they started building them. My 1949 CJ2a has one.

Yep. If memory serves the PCV system was invented for WWII tanks so they could more easily run in deep water.

[garmar]

Originally Posted by GRX

Yes. As you'd imagine, the problem gets worse as blow-by gasses increase with cylinder wear. How many of us have removed the PCV valve from an older running engine only to be treated to a nice big puff of smoke?

The engine in my first truck was so worn out. When I pulled the oil cap off with the engine running the blowby was so bad it felt like you were holding your hand over the exhaust.

['72customdeluxe]

Originally Posted by Lance-ftw

on the flip side though doesn't it end up getting gunk elsewhere because of where it's hooked up? I imagine some oil mist makes it back up into where it gets its vacuum.

Yes, quite a bit of oil gets sucked up. That's what a catch can is for

[cparman]

PCV valves relieve crankcase pressure. If you do not run one, sometimes you can have weird oil leaks. Seen this many times. Car comes in without PCV, or one that is not working. Oil leaks everywhere. Install PCV, ans wait a few days, and the oil leaks go away.

[Aberdare]

Originally Posted by GRX

Can you say sludge monster?

PCV = Positive Crankcase Ventilation. Basically it replaced the draft tube. The system utilizes intake vacuum to suck the compression stroke blow-by gases out of the crankcase; thus minimizing excessive carbon build-up in the oiling system.

In actuality... it is providing positive ventilation to keep your oil seals and gaskets from blowing out and leaking.

[brad_man_72]

less crankcase pressure more power also. This is why on some hi performance vehicles you see 1 large hose ran from each valve cover back to the ehaust. The exhaust will actually pull a vacuum on open header applications.

as stated before it exhausts blowby gasses increasing the life of your oil.

[El Jay]

Here we go. Andy (LHM) explains the PCV system with a great analogy that even I understood:;

Your crank case is filled with misted oil particles, fuel vapors, and residude from the conbustion that gets by your rings. All this is normal. When all this mixes together, along with water vapor from the humidity in the air, it becomes acidic, and contaminates your oil.
The PCV sucks all that crap out of the air that is trapped in the crankcase, and feeds it into the incoming air/fuel that is headed to the comustion chaimber for burning.
For simplicity, we'll compair the crankcase with your kitchen after you burned your dinner real good. I mean REAL good, thick smoke, hardly see across the room, let alone inhale.
1. You can open one window, and that'll let some air out.
2. Or you can open 2 windows... that's be better.
3. Or, you can open both windows, and place a window fan in one aimed out, to suck all the smoke out, while clean, fresh air comes in the other window on the other side of the room.

#1 is your engine with one breather.
#2 is your engine with 2 breathers.
#3 is one breather, and a PCV valve.

While this IS a polution control device, (and reqired federally in all 69 and later trucks, 64 and later in cars) it is one that has no performance killing drawbacks, and HELPS your engine last longer and run cleaner. And by cleaner, i don't mean smog, I mean crap in the oil, getting ground into the bearings and cylinder walls, causing poor oil pressure and less performance.

The way the factory did it on these trucks, was an oil fill, a PCV, ans a fresh air tube that was plumbed into a steel collar that went under the air filter. This is better than just a breather, this way, the fresh air being sucked into the engine, has been filtered by the large airfilter that is on top of the carb.

Installling 2 doesn't do anything good. If you have 2 on the same valve cover, with the fresh air inlet (breather or tube to the air filter) then it may do more than just one. If you install one PCV valve on each valve cover, with no vent, you can suck a gasket into the engine. Usually the intake end gaskets. If you do a PCV on each cover, and one vent, then the air inside that is supposed to flow from one side to the other gets disrupted. If you seal the engine off, no PCV, no vent, no road draft tube (pre PCV system) then you will end up building up positive pressure inside the crank case and spitting gaskets out.

Some remove them for aesthetic reasons, personally, I don't see them as being all that ugly. you can get aluminum ones from places like Jeggs or summit, and then steel braided hose if it pleases your eyes a little more, but in my personal opinion, it is a must have for anything but an all out show truck that rides in a trailer to get to the show.
__________________
70 C/30 Longhorn 425/TH350/4.10 (for now)
72 C/10 Suburban 402/TH400/3.07
Last edited by Longhorn Man; 05-11-2010 at 05:22 PM.

[raycow]

PCV was optionally available on Chevy trucks at least as far back as the early 50s. It was commonly specified on trucks that were to be used in low speed service, such as urban delivery, where the road draft tube is ineffective. Its value in reducing oil contamination, sludge and corrosion was already recognized long before any consideration was given to emission controls.

Ray

[lux]

I have to revive this thread, there is a lot of good info in here.

How do I know if my PCV is working?

I have what I think is a rear main seal leak on my LS1. I mentioned this to a friend. He asked if there was supposed to be a breather on LS1s, thinking that pressure was causing the oil to push out of the rear main seal. After a bit of research I've found no breather but a tube from each valve cover to a Y to the pcv then to the intake. I'm wondering if the pcv is good.

I also want to add a oil catch can and breather. Any wisdom on this would be appreciated as well.

Also there is always the chance that its just a bad rear main seal, but I'm learning all as I go.

[Stocker]

Originally Posted by lux

How do I know if my PCV is working?

http://www.dummies.com/home-garden/c...the-pcv-valve/

[RichardJ]

>>How do I know if my PCV is working?<<


The PCV System should maintain a slight, metered vacuum in the crankcase. I have one of these PCV Testers. When placed over the oil fill hole, the vacuum pulls the ball into the Green. You can do the same by placing a piece of paper over the fill hole. The slight vacuum should have neg. pressure to hold the paper on place or a little more. If no neg. pressure, try cleaning the PCV Valve.

Autozone has a nice how-to, test PCV page. https://www.autozone.com/repairinfo/...&subtitle=test

Pinching the vacuum hose, as shown at the bottom of their page should increase idle rpm by about 50 rpm.

Note: 1000 rpm is NOT idle rpm.

[lux]

Thanks RichardJ. I'll give that a shot tomorrow.

[beautimus]

it could also be a case of older and later parts. you may have an older block with a road draft tube , and a set of later valve covers .
(the older script covers just seem to get lost in the shuffle as time goes by.)
i have seen that combo before. also if you look at later cyl heads . in the area where the push rods go though the head on the way to the lifter (between the intake and exh. pushrods). you will see a small window, thats for pcv. the older heads did not have that window. the older heads will still breathe for pcv because of the space around each pushrod and thru the oil drain back ports . just throwing that out there.

[lux]

Originally Posted by beautimus

it could also be a case of older and later parts. you may have an older block with a road draft tube , and a set of later valve covers .
(the older script covers just seem to get lost in the shuffle as time goes by.)
i have seen that combo before. also if you look at later cyl heads . in the area where the push rods go though the head on the way to the lifter (between the intake and exh. pushrods). you will see a small window, thats for pcv. the older heads did not have that window. the older heads will still breathe for pcv because of the space around each pushrod and thru the oil drain back ports . just throwing that out there.

Thanks, but does that apply to my 2000 camaro LS1?
I think every thing but the headers are original to this motor.

[beautimus]

Originally Posted by lux

Thanks, but does that apply to my 2000 camaro LS1?
I think every thing but the headers are original to this motor.

oh sorry, no, i didn't catch on to the revitalized old thread thing, sorry. i thought that i was replying to the o.p. i dont know anything about the new generation of engines, my thought was specific to the old school stuff.
but ttt for ya, maybe some of the younger members can help out. tony

[lux]

I read the page on how to tell if the pcv is not working. I opened the oil filler cap and put a piece of paper over the hole. There was definitely no vacuum pulling it down, in fact there was a mist rising out of the oil fill tube. Guess I have a faulty pcv system. Which I'm sure could cause pressure in the engine and oil leaks. I'll get the pcv right, also put in an oil catch can then fix the oil leak if its still there.
Thanks a lot gentlemen, this site is such a great help.

[lux]

Well, I checked all the lines and the pcv and they all seemed fine. I changed out the pcv valve, it was only $3. I still feel no vacuum on the end of the tube from the intake and after the pcv. No vacuum at all, not even at high rpms.
I'm researching what to do next, If anyone can lead me in the right direction it would be much appreciated.

[davepl]

Keep in mind that the PCV system is designed such that your carburetor is calibrated for it. In other words, it expects that there is a certain controlled amount of air bleed.

That rate of flow is something you lose when you put in a generic PCV. There are more expensive adjustable ones, but then you have to know how to adjust them.