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Discussion Starter #1
I am going to replace my inlet manifold and Q-Jet for an Air Gap and Demon. The Demon has a large vacuum source
on the base but I would like to keep that for my PCV valve.
Can I use the vacuum source, circled in attachment, as a vacuum source for my brake booster?
 

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Sure you can, but I just T`d into the same line as the pcv on the rear of my Demon, I`ve ran it like this since I got the demon and haven`t had any problems.
 

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I would use the port you indicated. I've read that it isn't a good ideal to tap into the PCV line.
 

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I agree with MI2600. You should have a main source on the base of the Q-jet to use. Cutting & splicing Vacuum lines looks tacky under the hood on main lines unless you had no choice. But you do not want your PCV tapped into feeding other sources. Long term effect on proper ventilation.
 

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Discussion Starter #5
So I could swap them around then and connect the PCV to the manifold and the brakes to the carb base ?
This would be neater as I could turn the valve cover around and place the PCV valve at the back.
I´ve got a bunch of extra parts coming, one thing I´m going to need to use that manifold port is a half inch spacer, but I did´nt think I´d be using it.
How about if I left the PCV out and used a filter as used on the other valve cover ?
 

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Keep the PCV valve. This is one pollution control device that is actually worthwhile. There is an amazing amount of gasses generated in the crank case and the PCV vacuums them out and supplies whatever little BTU value they have to the engine. More importantly, they keep the engine outside clean. Without them, you need something like the old 'road tube' that dumps the stuff out onto the road.

Any port near the plenum under the carb is OK for either vacuum connection. Since the brake booster & distributor vacuum advance move virtually no gas, just seek a vacuum signal, they should be hooked in separately from the PVC which is looking to move volumes of gas, not develop vacuum.
 

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In my case I had no choice but to T it. The demon has 3 vacuum ports, 2 on the passenger side, ported not in use, manifold connected to vacuum advance. Rear port connected to power brakes, manifold source which is a 2 nipple fitting, one goes to the modulator valve and the other goes to the vent controls, leaving no where else to connect the pcv. I haven`t seen or found a 3 nipple screw in fitting for the intake that has a port big enough for the pcv, plus have room for the other 2 ports all in a rowe, I have seen them on seperate sides, but my pcv is on the rear passengers side, the same side the modulator line and vent controls are connected at. The inline check valve that comes on GM vehicles eliminates anything going back into the booster itself, it`s designed to close under no vacuum conditions to give some power assist in braking.
 
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