Valve Cover PCV and Vacuum Connections

[Thom71GT]

E-mail it to me. Thom@ttwatchworks.com It can be a fairly large file, I have dsl.

[Gary]

John,
You can upload the full size picture to the "Members Photo Gallery" and link it here. I had to limit the photo size in the Forum so it would not slow the load time too much. Just click on the link in the left column on the "home" page.

[jpiper]

VoodooU/Gary
I uploaded the file, as you requested Gary, in the Members photo gallery. Hopefully it will be of better quality for you VoodooU. Let me know the results.

[zephead69]

This is my first post, so excuse me if I seem a little slow...

I recently acquired a '72 GT that had a 32/36 Weber DFM (?-manual choke). The two inlet/outlets in the valve cover have just been left open, and I am not sure how, or even if, they should be connected. I understand that originally they fed into the snorkel-type air cleaner assembly, but now that I have only a simple air filter on top of the Weber, I am lost. Any input would be very helpful.

[kwilford]

Sorry for asking the obvious, but have you read this ENTIRE thread? There are two pages, and here's a link to an illustrative picture. After you do, and if you still have questions, ask away!

http://www.opelgt.com/photos/showphoto.php?photo=949

[kwilford]

And for what to do with the hoses that were formerly hooked to the Solex Air cleaner, and now don't have a home, go to:

http://www.opelgt.com/forums/showthr...&highlight=PCV

[opelgal33]

Mechanics 101 requested.


I am trying to read this thread and understand half of the stuff you guys are saying, but ain't gettin it

See I am looking around trying to find what comes out of the valve cover as far as lines running. I have none at the time and oil leaks galore. My engine has so many hoses floating around and I dont know where they go. I think some (ones on the drivers side of engine) went to the A/C something or nother that when there. Anyhow can you explain this in laymans terms

By the way I do have the piece of sh** solex still in mine, and yes the Weber is top priority. After I feed my kids, or do they really need to eat, awfully tempting

Jennifer

[opelgal33]

I am going to have to borrow a digital camera and take a picture of my carb.

I found the picture jpiper downloaded and mine does not look like this. Unfortunately I can't read some of the discriptions of the hoses.

I don't have the line from air filter
PCV something or other
on the"y" I have one going to distributor the other plugged
Brake Booster???
What is the hose above the "y" connection? I have nothing there either. just the nipple
no cannister vent line either.

Yikes, hows this thing run?

Jennifer, I will try to get a picture in the next day or two

[kwilford]

OK, first, kids need WAY less food than most parents seem to think. So Webers are more attainable than they appear!

Now, a layman's guide to PCV (Positive Crankcase Ventilation) and Opel valve cover hoses. I seem to have made a career on Opel PCV systems, and GT headlights. But I digress....

Internal combustion engines generate internal gases. Well, it happens from things like leaky piston rings and valve seals. If an engine was all sealed up, it would be like a big ballon. And after a while, it would go "pop". The gases would pressure up the crankcase and blow all the oil seals. BAD gases!

In the olden days, cars just had breather caps (or crankcase vents, in the case of post-war British cars) that allowed these gases to vent to the atmosphere. These gases have pollutants in them, such as unburned hydrocarbons. And oil, which dripped all over the sides of old British cars, even when their seals didn't leak. BAD olden days!

Then, some clever Engineer (hmm...) figured out that if you routed those gases to the intake manifold, they would burn up, and we would have a happier planet. So he (or she) invented the PCV system. Most cars, in the past thirty five years or so, use a PCV valve that connects to the intake manifold, where the inherent vacuum "sucks" the gases out of the crankcase and into the combustion process. It also requires a breather, to keep the crankcase from being sucked too hard (into a vacuum condition). The breather filter (usualy inside the air filter cannister) pulls clean air from inside the air filter, and the air goes into the valve cover (and hence the crankcase). On "Vee" engines, one side is the breather, and the other is the PCV valve. In-line engines usually have one fitting at each end.

At higher rpm (or as the engine gets old), the engine generates more gases than the PCV system can remove (Blow-by) and the breather reverses flow, and gases flow OUT the breather, and into the throat of the carb or fuel injection throttle body. Either way, the gases were burned. GOOD PCV system!

The PCV valve is usually stuck in the side of the valve cover, and is a combination check valve and metering valve. The check valve only allows gases to flow out of the valve cover, not in. And the metering function keeps too much air from being pulled OUT of the crankcase.

Now, our Opels have a slightly different system. Instead of a PCV valve, they use a metering orifice where the small hose connects the small hole in the valve cover to the PCV orifice at the intake manifold. This is the small metal tube just below brake booster fitting, as shown in jpiper's picture at:

http://www.opelgt.com/photos/showpho...t=1&thecat=500

So, the small hose is the equivalent of the PCV hose in most (especially North American) cars. But Opels of this era do NOT use PCV valves! The big hose, which is where folks seem determined to install PCV valves from their local NAPA dealer, is the equivalent of the breather. It is connected at one end to the air filter (to draw filtered air IN to the valve cover at idle, and out at higher rpm) and the other end to the big hole in the valve cover. DON'T install a PCV Valve here, as it will block the intended flow of air and crankcase gases, and cause the oil seals to leak even worse than they might already.

So, after this diatribe on the theory and operation of PCV systems, here's the scoop. Big hole in the valve cover connects to the similar size tube on the stock air filter neck (just before the dreaded Solex). If you have a Weber with the typical flat air filter, you need a fitting installed on the bottom to connect the big hose to. The little valve cover hole connects to the PCV orifice tube.

If you also want to know where the gas tank and charcoal cannister vent lines connect, the pages I mentioned previously have more on that topic.

HTH

[opelgal33]

Keith, Keith, Keith let me show you how it's done in "Laymans terms"


So what you are saying is that the little nipple by the brake hose and the distributer hose goes to the little hole in valve cover and the neck of the air cleaner has a big nipple that goes to the big hole. See thats how its done.

Just being funny. Ya'll have been doing this so long and or have some mechanical background that you can't bring yourselves to think there are idiots out there (like me) that will attempt to work on a car with no previous knowledge. Of course then again the way these cars tend to get butchered by the PO, there are more of us out here than you think.

I really appreciate all your help. I see where the hoses go that are missing. I know this is part of my oil leak problem. Maybe even the whole problem.

Ya'll will train me yet. Jennifer

[opelgal33]

Just when I thought I had it.

Lets see how many more times we (you, Keith) can go over this.

Let me tell you what I have, because it is not what you have.

I understand the "t" shaped piece that has a small opening going to the distributor ( which mine is plugged) The end of the "t" goes to brake booster, and the larger nipple goes to larger nipple on distributor. Also I see where large whole on valve cover goes to air filter.

Now comes the confusion. Under the "t" is another nipple very hard to see. I assume this should go to the small valve opening. Yet mine is attached to a metal tubing that goes back towards the firewall and down under the car?? And what about the vaccum advance, where does that go from the carberator?

my vent line from gas venting system that goes down the back end of the car all the way up front, is just hanging around in the nose of the car??

Sorry if you seem to be repeating yourself over and over.


Thanks Jennifer

[Gary]

Originally posted by opelgal33
So what you are saying is that the little nipple by the brake hose and the distributer hose goes to the little hole in valve cover and the neck of the air cleaner has a big nipple that goes to the big hole.

Just make sure the nipple the hose from "the little hole in the valve cover" goes to has a real small hole in it not a full size hole. The small hole helps to control (meter) the amount of vacuum to the valve cover.

[opelgt722002]

Gary, you wrote:
The small one connects to a metered orifice located on the intake either at the engine side below the carb base or is part of the brake booster vacuum fitting.

I just looked at the intake manifold on a 70 GT and it has a 90* fitting on the engine side instead of below the brake booster vacuum fitting. My 72 GT is on the outboard side.
Which year intake manifolds have the fitting on the inboard side and which on the outboard side?

[Gary]

I *believe* the early ('69 - '70) engines had the 90° fitting. The later ones had the metered nipple on the brake booster fitting.

[webster]

"Now comes the confusion. Under the "t" is another nipple very hard to see. I assume this should go to the small valve opening. Yet mine is attached to a metal tubing that goes back towards the firewall and down under the car?? And what about the vaccum advance, where does that go from the carberator?"

opelgal do you have an auto trans? because on my '72 auto that metal tube goes to the vac modulator on back pass side of trans.
and the fitting on the intake (brake booster connection has two little nipples not one ). the nipple below this on intake goes to the valve cover

[webster]

I have a great write up from OGTS on this subject but it's to large to download/or i dont know what i'm doing cause its not working. if anyone wants it e-mail me at
ptregan@hotmail.com

[opelgal33]

Yes your right there are two nipples on the "t" . One goes to the distributor and the other?? Are you saying that the little one with the tiny hole is the one that goes to the valve cover? I thought this one went to the small nipple on the distrib?




yes auto trans on 72

[webster]

The other goes to the vac modulator on the trans (tail end pass side) metal pipe that goes to fire wall e-mail me i'll send the write up it has all the pics you'll need to get it done

[opelgt722002]

Keith, you said:I tapped the valve cover with a 1/2 inch NPT tapered tap and bought a 1/2 by 3/8 brass barb fitting to connect the hose to . How much material would you estimate you had to remove inside the valve cover to enable you to tap the 1/2"npt?

[oldopelguy]

I always just ran the taps right in, 1/2"npt for the big hole and 1/8" for the small hole.

You can also get a pair of double nipples, shorten one side of each, and solder them in place. This gives a bit shorter profile (doesn't stick out as far) and will let you but the hose almost all the way up to the valve cover.