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Can anyone explain Vacuum please? This is what I know. I have a 350 in a 1968 Camaro. It might have a mild cam. I dont know anything about the engine.
I have power brakes and it needs to have vacuum to work
I also have an Edelbrock Carb that has a vacuum line to what I may call a PCV valve? (not sure what that does)
Now..... My Chevelle has a Vacuum line coming off the bottom of the air cleaner to a breather on the engine. This 350 in the camaro does not.
I want to clean up the engine compartment to the Camaro and put on a new Air cleaner and filter. what does it all mean, and how should I do this. I dont want to schedule a tune up until I make all these mods.
Can anyone help out on this
 

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Donnie the PCV is for oil burn off and connects from valve cover to center port of Edelbrock carb. You need to install a vacuum adapter to the intake manifold for Automatic transmission and power brakes.

I have plenty of pics.
 

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The hose from the air cleaner to the valve cover is the fresh air intake for the positive crankcase ventilation (PCV) system. Your Camaro may just have a breather in the valve cover opposite the one with the PCV in it. That is acceptable (but not preferable to me) as long as the breather has a filter element in it.

Vapors get sucked from the crankcase through the PCV valve on one side, and fresh air replaces them on the other side. You have to have a fresh air supply. Think of sucking on a straw from one end, and then putting your finger over the other end what would happen.

In the past the engine was basically open so that vapors/gases/etc from combustion that made their way into the crankcase just vented out to atmosphere. PCV was introduced as an emissions control method to instead suck them into the intake and burn them.
 

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PCV is an acronym for Positive Crankcase Ventilation. It was designed to work best when combined with an air cleaner breather. There should be a PCV valve located in a grommet in the drivers side valve cover with a vacuum line that runs to manifold vacuum. The valve allows a limited amount of manifold vacuum to suck or pull crankcase vapors out of the engine and then the get burned along with the incoming air/fuel mixture as the engine is running.

There should be another rubber grommet in the passenger side valve cover with a larger diameter hole than the PCV valve grommet that a breather cap plugs into. The breather cap should have a hose that runs from itself up to a nipple on the underside of the air cleaner. This breather allows the passenger side of the engine to have additional crankcase ventilation when necessary and/or fresh air to be pulled in to replace what the PCV valve sucks or pulls out of the crankcase.

Depending on the condition of the cylinders, pistons and rings, some engines will have more or less blow by. More blow by means more crankcase ventilation is going to be necessary. At idle, the breather may be allowing fresh air flow into the crankcase but at higher rpm's when more blow by is occurring, the breather actually allows the crankcase pressure that can't make it out the PCV valve to be pulled into the engine through the breather and then be burned with the air/fuel mixture.

The PCV system replaced the old down draft tube systems of earlier engines that were "less friendly" to the environment as they just released all the crankcase gases (and quite often oil) into the atmosphere and onto the ground. You'll always have some amount of blow by in any engine (the less the better) and thus an engine needs a way for the crankcase to vent or the engine crankcase pressure will create a way at the weakest link which will usually be one or more gaskets weeping, leaking or out right blowing.
 

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The hose from the air cleaner to the valve cover is the fresh air intake for the positive crankcase ventilation (PCV) system. Your Camaro may just have a breather in the valve cover opposite the one with the PCV in it. That is acceptable (but not preferable to me) as long as the breather has a filter element in it.

Vapors get sucked from the crankcase through the PCV valve on one side, and fresh air replaces them on the other side. You have to have a fresh air supply. Think of sucking on a straw from one end, and then putting your finger over the other end what would happen.

In the past the engine was basically open so that vapors/gases/etc from combustion that made their way into the crankcase just vented out to atmosphere. PCV was introduced as an emissions control method to instead suck them into the intake and burn them.
Steiner, looks like were were both replying with more detailed answers at the same time :)
 

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Steiner, looks like were were both replying with more detailed answers at the same time :)
Yeah, I hate when that happens when I do the same thing. Can tell just by looking that you were taking time to type out a good explanation while I was posting. On a bad day though I might say, what, is there an echo in here?
 

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Discussion Starter #9
That is why this site is so awesome. There is so much knowledge here. Bear with me... I am going to try to draw a picture for you to comment on if you don't mind
 

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Discussion Starter #10
vacuum drawing.jpg

This illustration is what I am reading. I understand the fresh air and the air passing throught the PCV valve. How does the Power brake booster fit into the equation? My 65 Chevelle has a big block 454. I did not put in the engine. It is set up as you guys have described the best installation. however the cam in the big block did not allow enough Vacuum so an electric vacuum pump was installed for it only. what would be the proper plumbing (so to speak) for the brake booster vacuum
 

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Discussion Starter #13
Mr Steiner. That is a great picture. That is the carburetor. Can I also assume that the small drawing I posted is correct? The transmission is a 4 speed.
 

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You bet. Yep, diagram is good but typical install is PCV in front driver side and fresh air in rear passenger side.

If yours has the plug in it, you can get at 1/4 NPT nipple at about any store that carries plumbing supplies like ACE etc.
 

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Discussion Starter #15
Thank you everyone. Thank you for your time. Great site.
drive careful.
Jeff, maybe we will see each other soon? Rocky Hill isnt too far away. Maybe in Manchester????? I believe that show is coming up soon
 

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Don't you all love threads like this?:thumbsup:
 

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Discussion Starter #17
One quick curve ball to throw in here. I followed out most of the Vacuum hoses, etc. Made a small shopping list for new breathers and hose and fittings. As I traced things out I found that there is a canister under the driver front fender. (to store extra vacuum?) There is also a 1/4 inch hose from that canister that goes through the firewall into the car under the dash. I had not mentioned that this is but not hooked up A/C car. Any thoughts before I remove something that I should not?
 

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One quick curve ball to throw in here. I followed out most of the Vacuum hoses, etc. Made a small shopping list for new breathers and hose and fittings. As I traced things out I found that there is a canister under the driver front fender. (to store extra vacuum?) There is also a 1/4 inch hose from that canister that goes through the firewall into the car under the dash. I had not mentioned that this is but not hooked up A/C car. Any thoughts before I remove something that I should not?
Can you post a pic of this ? The only canister I can think of on the driver's side would be a washer bottle for the wipers; but the hose would not go through the dash.
 

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Depending on the year, it sounds like that canister could be a vacuum canister for the Rally Sport vacuum operated headlights but a picture would confirm that or correct it?
 

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Yeah no he is talking about a canister, drivers side front fender, tucked under and near the firewall. My car also has one. I believe the purpose is to assist the actuation of various vents and dampers in AC cars... Mine all have 40+ years of age on them and are basically frozen up so it makes no difference. Donnie just be sure it isn't connected to your carb and you should be good in terms of proper motor performance.
 
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