Author Topic: Intake manifold vacuum source on integral head  (Read 2825 times)

Offline bnoggle

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Intake manifold vacuum source on integral head
« on: May 28, 2017, 10:36:14 AM »
Can anyone tell me where the intake manifold vaccum source would be on a chevy 250 integral head. The engine is out of a 1983 chevy c-10.

Offline zieg85

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Re: Intake manifold vacuum source on integral head
« Reply #1 on: May 28, 2017, 11:44:12 AM »
Center of intake manifold right below the carb for the power brake booster
Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline bnoggle

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Re: Intake manifold vacuum source on integral head
« Reply #2 on: May 28, 2017, 09:31:26 PM »
Would that be the same on a truck without power brakes?

Offline zieg85

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Re: Intake manifold vacuum source on integral head
« Reply #3 on: May 28, 2017, 09:38:30 PM »
Yes but what vacuum are you looking to hook up?  PCV, distributor?  I have a 1984 4.1L engine on a stand to look at
Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline bnoggle

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Re: Intake manifold vacuum source on integral head
« Reply #4 on: May 29, 2017, 12:35:43 AM »
I'm actually not looking to hook anything up, I'm just trying to follow the vacuum diagram printed under the hood to find where there should and shouldn't be hoses. Someone "redesigned" the vacuum system in this truck, and I was having trouble identifying what components went where. I think it is correct now as the motor is running smoother than ever before, then again it may be the new head gasket, exhaust gasket, belts, water pump, valve train, carburetor rebuild, and ignition solenoid I have installed in the last few days.

Offline VileZambonie

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Re: Intake manifold vacuum source on integral head
« Reply #5 on: May 29, 2017, 09:11:41 AM »
There are several different vacuum diagrams for this depending on how your truck was equipped. Federal or Cali emissions, Auto or Manual Trans, High alt etc.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline bnoggle

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Re: Intake manifold vacuum source on integral head
« Reply #6 on: May 29, 2017, 09:55:49 AM »
Its federal emissions, and a thm700r4 automatic transmission. No power steering or power brakes. It does not have AC, or anything that would be considered an upgraded feature in 1983.

Offline VileZambonie

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Re: Intake manifold vacuum source on integral head
« Reply #7 on: May 29, 2017, 02:28:56 PM »
This is what should be on your VECI label
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              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline bnoggle

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Re: Intake manifold vacuum source on integral head
« Reply #8 on: May 30, 2017, 12:47:22 AM »
Ok, thanks, that's very helpful since it does not match the one under my hood, but it makes a lot more sense for the number of vacuum hoses I have. It turns out the original problem was a leak at the manifold vacuum source, once I found it. Now I have it to the point that it runs perfectly until it gets warmed up, and then it starts to run rougher like there is a vacuum leak. I have tried plugging lines to isolate the problem, but have had no luck. Does anyone have any guesses what may be leaking? Are there any common sources in our trucks that are prone to vacuum leaks? I am assuming it is something that is controlled by the thermostatic valve on the water neck, but I'm not sure what component it may be.