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Vacuum lines and EGR
#748520 May 17th 2019 1:28 pm
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Hello all, newer here. Bringing an old Class B, my first Chevy, back to life. I pulled my emissions crap off, capped the manifolds, now I’m re doing the vacuum lines. I’m wondering if someone could help with a few questions:

Do I simply delete all vacuum lines that went to the emissions crap, reroute them as if they were never there?

Most of these lines are turning to dust when pulling them off, anyone know the sizes? I have the vacuum diagram but it doesn’t show them. Looks to be 2 or 3 different sizes. The only one in good shape is the brake booster.

Are the Haynes or Chiltons manuals worthwhile for this van?

Thank you. I’ll try to post a couple pics of what im looking at now.

Re: Vacuum lines and EGR
84G20HiTop #748521 May 17th 2019 1:35 pm
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Few images.

Attached Files ADC6B2BF-18D3-475C-81E9-95802FAA478D.pngF993684F-514D-440E-895B-E9862B42E09A.png827ECE38-8FB4-43AD-A161-0EE658264444.png9B7AC680-1AFB-4EF8-846F-8F260EF7768A.png
Re: Vacuum lines and EGR
84G20HiTop #748570 May 18th 2019 5:46 pm
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Well reading that chart, or learning to read it rather, was pretty interesting. Going from engines that create air with a mounted air compressor (DD’s, S60’s or ISX’s) to one that creates used vacuum was fun. Chart was not hard to read. I just picked an accessory and worked to the end of the run then went to another one until they all let up at the carb. Even hoses that should’ve been there were not there before I went in. Fun. I also removed the smog pump and manifold injection valves and put in 1/2” (x18 or 20, can’t remember which) plugs from Lowe’s. I left the EGR for now because I read it may need a tune or some other cats. What I read about someone removing all but 1 or 2 vacuum lines was from a tuned and modified engine.
Thanks for the help.

Attached Files 0DA24AE7-E7E5-481D-B3F6-79FBF14FD2A3.png
Re: Vacuum lines and EGR
84G20HiTop #748641 May 20th 2019 2:45 pm
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i am curious to know this as well. I would love to delete as much vacuum stuff as I can. my van is a 79 with the 350 SBC and all the smog stuff pulled off the manifolds, too.


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Re: Vacuum lines and EGR
84G20HiTop #748642 May 20th 2019 2:46 pm
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what chart were you using?

Re: Vacuum lines and EGR
84G20HiTop #748643 May 20th 2019 3:10 pm
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FYI- the air injection is more important to te catalytic converter on a cabureted engine than is the EGR valve, but both are beneficial to the engine and should be left intact and functioning.


Windows- they're what make a van worth owning!
Re: Vacuum lines and EGR
84G20HiTop #748662 May 20th 2019 10:17 pm
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Air injection is an emissions thing only. In 1967 Pontiac had A.I.R. on California cars , which had closed chambers heads. In 68, the heads went to a open chamber design and the "smog pump" was no longer needed and was never seen again on a Pontiac.

Pinch off the vacuum line to the EGR valve while the engine is running. If the idle changes-the valve is bad. Then pull the valve and install a block off plate. If the vehicle runs "different"-the valve is also bad but leaking externally.


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Re: Vacuum lines and EGR
84G20HiTop #748663 May 20th 2019 11:40 pm
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But air injection allows a cleaner burn of the exhaust in the catalytic converter and helps a converter survive longer behind a carb. Air injection helps prevent the overheating of the catalyst and the breakdown of the matrix which leads to clogged cats and exhausts.

EGR helps with controlling engine park knock and is a useful tuning tool.


Windows- they're what make a van worth owning!
Re: Vacuum lines and EGR
NEmery #748664 May 21st 2019 12:01 am
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Originally Posted by NEmery
i am curious to know this as well. I would love to delete as much vacuum stuff as I can. my van is a 79 with the 350 SBC and all the smog stuff pulled off the manifolds, too.


I believe there were some lines under the hood that were missing and not on the chart. I got the Tip In Sw with the two wires and the Trans vac switch with the green and blue(?) wire and a small vac line coming out of the back.

What I don’t have, and is not on the diagram XDK (pic) is the vacuum reservoir to the T and beyond.

Also, what else is not on the diagram is the main engine vacuum having two hoses off of it. One is on the diagram, the other goes to a T, then to the front under the hood somewhere and to the second pic I have. In this case, it broke off on a minor brush. Any idea what that is?

Attached Files 0160C9F2-32AE-4B87-867D-07A727EA6144.pngD710B436-9173-4CE5-9836-6D16995FA192.png
Last edited by 84G20HiTop; May 21st 2019 12:13 am.
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