Vacuum diagram for 1977 bu

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Vacuum diagram for 1977 bu

Post by nowforever13 on Sun Sep 27, 2015 7:25 am

Anyone know where i can get a vacuum diagram for the 77 350 malibu, im needing to make my vents work and i cant figure out where the hoses go
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Re: Vacuum diagram for 1977 bu

Post by ant7377 on Sun Sep 27, 2015 9:23 am

The ball on the passenger side near the blower motor resistor gets a line from manifold vacuum on the out side port and another from the dash on the inside port
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Re: Vacuum diagram for 1977 bu

Post by Mcarlo77 on Sun Sep 27, 2015 9:38 am

I had attached a diagram on this previous thread that might help:

http://www.g3gm.com/t7015-climate-control-vacuum-lines?highlight=vacuum+diagram

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Re: Vacuum diagram for 1977 bu

Post by nowforever13 on Sun Sep 27, 2015 7:27 pm

Alright ive got the pink amd black hose going to the water connector valve and the white black going to the ball and the other going to the tee, ive got a hose going from the tee to idk where but someone told me it goes to something on the intake ive got one big hose going from the ball to a port on my carb, that.leaves one hose missinv from. the tee and the hose that connects to somewhere on the intake
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Re: Vacuum diagram for 1977 bu

Post by ant7377 on Sun Sep 27, 2015 7:30 pm

The one going to the carb. Is it at the base of the carb ? Is there vacuum there at idle? You need to have vacuum all the time for that hose. The other hose goes from the ball into the car under the dash to the diaphragm. There might be a really small hose going to the heat riser valve.
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Re: Vacuum diagram for 1977 bu

Post by nowforever13 on Sun Sep 27, 2015 7:47 pm

I have 3 hoses that come through my firewall, on connects to heat riser, on goes to vaccum ball and one goes to a white tee connector with 3 nipples i have 2 hoses connected to the tee, one of the hoses is one that comes through the fire wall, the other is one that idk where it goes, on the vacuum ball ive got a big hose going to a port on the passenger side of the carb its a holley 750 dp its under the vacuum choke bowl
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Re: Vacuum diagram for 1977 bu

Post by Mcarlo77 on Sun Sep 27, 2015 9:57 pm

Here's what you need for correct setup under the hood.  This is how my all-original '77 Monte is plumbed:

- As stated, you have three small vacuum lines coming out from the firewall.  One goes to the plastic tee, one goes to the water control valve and one goes to the vacuum ball.
- The tee also has two larger nipples...one for the hose that also runs to the vacuum ball and the other goes to the intake manifold vacuum tree.  No hose should be running to the carb on a stock setup.  Plus, heat riser hose comes from a ported switch that is threaded into the thermostat housing...again, that's stock setup.


Last edited by Mcarlo77 on Sun Sep 27, 2015 11:28 pm; edited 1 time in total
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Re: Vacuum diagram for 1977 bu

Post by ant7377 on Sun Sep 27, 2015 10:07 pm

I thought your car was stock (malibu) you can probably just cap off the extra ports you have open in the intake or connect a vac line to on and cap off the one on the Holley. They did stuff like that so it wouldnt blow out of the vents at wide open throttle or other emission events.
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Re: Vacuum diagram for 1977 bu

Post by nowforever13 on Mon Sep 28, 2015 12:00 am

I know the smallest hose goes to the water control/ heat riser, i dont have an intake vacuum tree? My intake isnt stock its a edelbrock torkfer2 on a gm goodwrench 350 engine, i just need to make my defrost work.. Its a bitch trying to sort it out. Just tell me what needs to be hooked up where and where the 3rd hose on the plastic tee is and if the large vaccum ball hose doesnt go to the carb where does it go?
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Re: Vacuum diagram for 1977 bu

Post by ant7377 on Mon Sep 28, 2015 6:03 am

It just needs to connect to manifold vacuum, if the port on the carb is the only spot to get manifold vacuum use that. Mine is tee'd into the line from the transmission modulator then to the carb.
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Re: Vacuum diagram for 1977 bu

Post by nowforever13 on Mon Sep 28, 2015 8:28 am

Okay and what about the 2nd line on the tee? To i just tee it into the carb aswell? Amd plug off the 3rd nipple?
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Re: Vacuum diagram for 1977 bu

Post by Mcarlo77 on Mon Sep 28, 2015 9:55 am

You only need one vacuum source.  Utilize your existing 3-way tee by connecting the vacuum source hose to it, the small hose from the firewall as before, and run a third hose to the vacuum ball.  Easy...done!
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Re: Vacuum diagram for 1977 bu

Post by nowforever13 on Mon Sep 28, 2015 10:58 am

It worked!, i connected a hose from the vac bal to the carb and a hose from the tee to a spot on the carb, then i plugged off the third hole as it wasnt used... It only works when its started and works better when going down the road.. Its super hot too. Cant complain lol. First time its worked in almost 17 years
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Re: Vacuum diagram for 1977 bu

Post by pila on Mon Sep 28, 2015 9:01 pm

Good to hear it works !! Very Happy

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