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Discussion Starter #1
My brother has a 68 El Camino with a 350 motor that the PCV valve has been deleted and a breather has been placed on each valve cover.... he has been told that the PCV valve is not necessary on his classic car. What is the opinion out there of the PCV delete. Especially on our Gto‘s. I have a 66 Gto with a tri-power.. Delete the PCV valve and put another breather on one of the valve covers? I’m thinking not!
 

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I’m not in favor of that, you need that air draw from a pcv to relieve that pressure Or your dipstick and seals are going to tell you they don’t like it either
 

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Crank case ventilation is necessary to remove blow by gases, condensation, contaminated and dirty oil and vapors that destroy an engine. Back in the 30’s 40’s and 50’s all the cars had a “road draft tube” I had cars with it and am sure many of the guys did.

it was very inefficient at the given task as the rubber tube did not work at idle and only pulled a “draft” on the crankcase at speed. It laid an oil slick of crud down the center of all the roads and was an open vent to the crankcase at the bottom of the engine, sucking the vapors out.

The PCV system was actually invented by GM engineers in WW2, GM built the tank engine and they were stalling in the rivers in Europe because water would back up thru the draft tube. They could not eliminate the tube, or just leave a breather on top, because that would not work. Atmospheric pressure is at work on the breather 14.7 PSI as a constant, so it let’s air in, but not good for ventilation.

so they developed a simple system that would positively ventilate the crankcase by vacumn and establish a closed system that would not allow river water in and would be more efficient than the draft tube.

The PCV, vacumn ventilates the crankcase, breather(s) let fresh air in.

In the early 60’s the G asked GM to share the invention with the automobile manufacturers assn because it ALSO helped with emississions, because it burned up the crankcase vapors in the intake and engine.

So understanding that it was not developed for emissions is important as many believe that and then want to reject the valve as unnecessary. Second is to believe that you can use half of an engineered system, just breathers, and it works fine. It doesn’t.

only breathers gives you pressure on both sides, atmospheric on the breathers and crankcase pressure inside, how can that be efficient? What happens is eventually as you accelerate the crankcase pressure overcomes the atmospheric pressure and blows oil out of the breathers, your seals and gaskets, because no pressure was ever relieved.

Racers will put vacumn pumps and catch cans on the crankcase, and reduce the pressure inside to 8 to 10 Hg, remember piston rings going down create pressure too. And if you have a big vacuum there they don’t work as hard.But it sucks to much oil out for a street car so don’t do that.

The best thing is to add an ME Wagner dual flow PCV which pulls a crankcase vacumn of 1 to 3 Hg 99% of the time You cannot beat that. But even if you don’t use the Wagner use a PCV, you might get a vacumn 30% of the time from that $5 valve made somewhere near Kathmandu.But still better than breathers alone.

your engine will thank you and run better and last longer, it wants to exhale, just like you!
 

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You can usually get away with 2 breathers on a SBC, but I would not run that setup long term on a Pontiac engine.
 

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Discussion Starter #5
Thank you very much for your replies. I have another thought. Given your replies in your comments I’m wondering if you block off the PCV valve and just put a couple vents on your valve covers if you are somehow either robbing the vacuum or not creating enough vacuum for your transmission to shift properly. I noticed riding in my brothers 68 El Camino that it shifts slow.. with light pressure on the Excelerator. If you put a little more acceleration it will shift kind of hard but I think that’s because he has a shift kit in it. I know I’m asking these questions about a Chevy so bear with me buddy. LOL my brother said I should get rid of the PCV valve on my GTO. Don’t think I’m going to do that. But anyway what’s your thoughts on the vacuum issue related to the transmission when you Delete the PCV valve.
 

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Unrelated, what is related is the transmission vacumn modulator. Changed one yesterday on my TH350. That works of course off MANIFOLD vacumn..which is usually 10 to 20 HG.

crankcase vacumn is so minimal 1 to 3 Hg, you will not run anything with that.

The trans vacumn modulator is adjustable with a screwdriver in the stem. It keeps low speed shifts shorter or longer. Low speed, when there is vacumn, so the car shifts thru the gears at lower speeds. When you put the pedal down hard, vacumn drops out and the modulator does nothing, the shifts should be longer in duration then as the modulator is not effecting them.

This is a totally separate vacumn system from the PCV. The modulator costs about $14 is held on by one bolt and has a vacumn line to it on top rear of trans. You a pan if you pull it out it will drop about a pint of trans fluid when you do...make sure you getout the old Orin’s.

easy job probably fix that problem.

everybody sees things differently, but the PCV system was designed by GM engineers to use MANIFOLD vacumn to clear out the crankcase vapors and blow by and crud. The breather is for letting fresh air in, not for clearing vapors out.

Think of it this way with just breathers and atmospheric pressure pushing on them at a constant 14.7 PSI, the crankcase building internal,pressure from the downward stroke of the pistons where is the ventilation?........in your mind maybe, but not in your crankcase.

The pressure eventually builds inside under acceleration, overcomes atmospheric pressure on the breathers and blows oil out your breathers and seals etc. that is not ventilation.

when the strong 10 to 20:eek:r more Hg vacumn pulls through the PCV it is strong enough to drop the pressure in that big chamber to 1 to 3 Hg......and that vacumn is an “absence or pressure” and that lets fresh air in....and prevents it from blowing out your seals and gaskets.

Run a good PCV, the Wagner is the best hands down, you will feel your car engine run better when properly and positively ventilated.
 

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PS earl your brother was told ..”.PCV is not necessary on a classic car”.....another guy who believes that crankcase ventilation is an emissions invention and does not know that all internal combustion engines must have the crankcase ventilated so they don’t destroy themselves......

but hey, he saw a racer do it.....and it has 2 breathers so it must work......
 

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Thank you gtoearl for your post. There has been a couple PCV posts lately. This one got me investigating PCV though. I never thought of it as a tunable system. The stock setup is dependent on the engine vacuum. If that is no longer producing much vacuum due to modifications there maybe an issue and you have to retune it to what you have now..There are engine builders out there that will run down the benifits of case ventelation, whether its by manifold vacumm, vacuum pump or the affect of using a dry sump oil system. I didnt know it cost a racer horsepower if its not vented well. I cant tell you how many engines I have seen covered in oil from the valve cover vents. Usally the same car had oil leaks other places.I never really took the time to think it was not normal wear. I did run into the draft tube situation on my Mercury and a couple tractors. I like the PCV in the valley tray it hides it some and seems to be a better placement. That is where the draft tube was on the old Merc the rear of the intake manifold. On the intenational inline six the draft tube is on the side off the block. Oh what a mess that makes. I was like alot of people that thought it was for polution.


I guess I will be keeping an eye on all my PCV systems rom now on.
.
 

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67 ventwindow, ..I love vent windows and always have....!Try one of those ME Wagner PCV valves,...they are $129..much more than a $5 steamed steel PCV with a spring. They are engineered from billet aluminum and have dual circuits for idle and cruise tunable to your engine with a vacumn gauge. I use the Wagner and recommend it to all my hot rod buddies,..usually when I curve their distributors!

It is like curving your distributor, or curving your carb fuel mixture. It makes a world of difference with a mod that you can do at home, no major engine work and saves your motor makes it run stronger and cleaner. Add a catch can also even better. All that road draft tube crud is now more efficiently taken out of the crankcase and either burned up or later drained out of the catch can. You must use the ME Wagner on a baffled valley pan or valve cover or it will pull too much oil,...because it is so efficient. A stock Pontiac valley pan is baffled. But aftermarket ones sometimes are not.

You can run the PCV in the valley pan or a valve cover, as long as it is baffled. The breather does not have to be baffled. Just let that clean air flow right in!

Just a not on valve cover breathers, I use a K&N, they make a-miniature breather For the valve cover that looks just like a big air cleaner one. Those chrome ones with the small row of holes at the bottom and stuffed with a Brillo pad...look pretty..but the K&N filters the air real clean, let’s in more air because it has a bigger filter area and is easier to clean and reusable.....

Chrome will really not help your engine internals and performance!

so I try to make it the most efficient going out with the ME Wagner and catch can, and the cleanest Most efficient going in with the K&N..

you can use two breathers, even two PCV’s but you cannot eliminate all breathers or all PCV’s

it won’t work...even if you think it does...
 

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I agree with Lemans Guy re: the Wagner valve. I just added one to my engine and it made a huge improvement. I've got an Olds 455 with a mild cam upgrade and Edelbrock Performer intake/carb. Power was pretty decent but it felt restricted somehow. It stumbled at acceleration, had harsh smelling emissions, and two small oil leaks I couldn't get rid of. I read about others who used the valve to cure the same frustrations and figured I'd give it a try. Really glad I did. I highly recommend it to you and your brother. Good luck.
 
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