Vacuum lesson please - Team Camaro Tech
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post #1 of 23 (permalink) Old Jul 15th, 14, 06:45 AM Thread Starter
Donnie
 
Join Date: Jul 2014
Location: Connecticut
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Vacuum lesson please

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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post #2 of 23 (permalink) Old Jul 15th, 14, 06:49 AM
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Camarodude67
 
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Re: Vacuum lesson please

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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post #3 of 23 (permalink) Old Jul 15th, 14, 06:53 AM Thread Starter
Donnie
 
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Re: Vacuum lesson please

Where do I find you pics Jeff
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post #4 of 23 (permalink) Old Jul 15th, 14, 07:14 AM
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Steiner
 
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Re: Vacuum lesson please

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.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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'69 Camaro Beater-SFT 327-M20-Moser 4.10-sold
'02 Z/28 vert-stock-sold and totaled
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post #5 of 23 (permalink) Old Jul 15th, 14, 07:23 AM
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Scott
 
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Re: Vacuum lesson please

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.

69 Camaro Z/28 RS, original Azure Turquoise, M21 & 3.73 12-bolt posi. NOM 406ci, AFR 210 heads, Straub hyd. roller cam & Dynatech 1-3/4" > 1-7/8" headers, QuickFuel 750 Annular. Photos at:
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post #6 of 23 (permalink) Old Jul 15th, 14, 07:25 AM
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Scott
 
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Re: Vacuum lesson please

Quote:
Originally Posted by Steiner View Post
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

69 Camaro Z/28 RS, original Azure Turquoise, M21 & 3.73 12-bolt posi. NOM 406ci, AFR 210 heads, Straub hyd. roller cam & Dynatech 1-3/4" > 1-7/8" headers, QuickFuel 750 Annular. Photos at:
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post #7 of 23 (permalink) Old Jul 15th, 14, 07:57 AM
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Steiner
 
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Re: Vacuum lesson please

Quote:
Originally Posted by NH69Z28RS View Post
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?

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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'69 Camaro Beater-SFT 327-M20-Moser 4.10-sold
'02 Z/28 vert-stock-sold and totaled
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post #8 of 23 (permalink) Old Jul 15th, 14, 08:13 AM
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Camarodude67
 
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Re: Vacuum lesson please

Donnie, Pics sent to you...
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post #9 of 23 (permalink) Old Jul 15th, 14, 08:25 AM Thread Starter
Donnie
 
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Re: Vacuum lesson please

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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post #10 of 23 (permalink) Old Jul 15th, 14, 08:45 AM Thread Starter
Donnie
 
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Re: Vacuum lesson please

Click image for larger version

Name:	vacuum drawing.jpg
Views:	93
Size:	42.2 KB
ID:	79098

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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post #11 of 23 (permalink) Old Jul 15th, 14, 09:51 AM
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Camarodude67
 
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Re: Vacuum lesson please

is this a 4-speed or Automatic? The vacuum port is on the back on the intake and you need a dual feed vacuum port connection, 1 for the automatic transmission and 1 for the brake power booster.

http://www.ss396.com/camaro/APN-0238.html
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post #12 of 23 (permalink) Old Jul 15th, 14, 10:07 AM
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Steiner
 
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Re: Vacuum lesson please


'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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'69 Camaro Beater-SFT 327-M20-Moser 4.10-sold
'02 Z/28 vert-stock-sold and totaled
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post #13 of 23 (permalink) Old Jul 15th, 14, 10:12 AM Thread Starter
Donnie
 
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Re: Vacuum lesson please

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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post #14 of 23 (permalink) Old Jul 15th, 14, 10:25 AM
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Steiner
 
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Re: Vacuum lesson please

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.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

'69 Camaro Beater-SFT 327-M20-Moser 4.10-sold
'02 Z/28 vert-stock-sold and totaled
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post #15 of 23 (permalink) Old Jul 15th, 14, 10:36 AM Thread Starter
Donnie
 
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Re: Vacuum lesson please

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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