Author Topic: 318 vacuum hose routing  (Read 8591 times)

Offline burdar

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318 vacuum hose routing
« on: May 13, 2012 - 12:05:32 PM »
During disassembly I mady myself a diagram of where the charcole canister hoses go.  I didn't make a diagram of where all the smaller hoses go.  Is there a diagram of these hoses in the FSM?

There are only three vacuum nipples on the carb.(not including the one for the choke pull-off)  A vacuum line comes out of the EGR valve and goes into a "T".  One hose goes to a carb nipple, the other goes to the NOX valve on the firewall.  I don't know where the other end of the NOX valve connects to.

There is a nipple at the back of the carb.  I'm thinking that may be for the dist vacuum advance.  I think a line should go from that nipple to the vacuum control valve on the firewall(340's don't have that valve) and then back to the dist. 

There's only one more nipple on the PS side of the car.  The NOX valve has to get hooked up somewhere as well as the line from the air cleaner.  I didn't think there was another T involved but maybe there is.  :dunno:  :clueless:





Offline Jamiez

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Re: 318 vacuum hose routing
« Reply #1 on: May 13, 2012 - 12:46:33 PM »
 The 74 FSM does..... But that has an OSAC mounted on the air cleaner so it's probably not what you need

Offline Chryco Psycho

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Re: 318 vacuum hose routing
« Reply #2 on: May 14, 2012 - 09:10:06 AM »
never seen the vacumm advance nipple out the rear of a carb , is it a 2 bbl ?

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Offline burdar

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Re: 318 vacuum hose routing
« Reply #3 on: May 14, 2012 - 03:49:30 PM »
Yes, it's a 2-barrel carb.  Looking at one picture I have, it doesn't look like anything is connected to the vacuum control valve.  That can't be right though.  I remember lines being connected there.  If it wasn't used, they would have just put a plate on the firewall like the 340's.

Here are a couple of pics of the carb.  The vacuum hose that comes out of the PS...and the one coming off the EGR valve, go into the wire holders on the valve cover and I can't tell where they go for sure.




Offline Chryco Psycho

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Re: 318 vacuum hose routing
« Reply #4 on: May 14, 2012 - 09:40:24 PM »
I would say the one in the second pic high up marked possible NOX valve is the dist advance , it is easy to check , it should have no vacuum at idle & increase with RPM .
The one on the rear should be manifold vacuum & may go to the nox valve

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Offline Jamiez

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Re: 318 vacuum hose routing
« Reply #5 on: May 14, 2012 - 10:10:11 PM »
The 1974 carb.  Maybe it'll help?


Offline burdar

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Re: 318 vacuum hose routing
« Reply #6 on: May 14, 2012 - 11:25:25 PM »
Ok, it's becoming a little clearer.  I must have drawn my diagram wrong.  Here is a picture of the NOX valve.(OSAC) I guess it's labeled DIST and CARB.


So, Chryco was right, the port on the PS goes to the OSAC valve and then down to the dist.  The small port at the rear is labeled air cleaner in the 74 FSM. 

Now, what does the EGR valve connect to?  The part to the left of the OSAC is labeled "controle valve".  I looked on "allpar" and it says the EGR can use a vacuum amplifier.  Is that what that thing is?  If the vacuum line goes from that "T" to the controle valve, where does the other end go?

Offline Bullitt-

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Re: 318 vacuum hose routing
« Reply #7 on: May 15, 2012 - 08:10:52 AM »
Maybe this will help


Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
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Offline Bullitt-

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Re: 318 vacuum hose routing
« Reply #8 on: May 15, 2012 - 08:26:47 AM »
Appears the second nipple on the temp.cont.valve is for a "filter"


Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
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Offline burdar

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Re: 318 vacuum hose routing
« Reply #9 on: May 15, 2012 - 11:50:05 AM »
 :eek2: :worshippy :worshippy :worshippy :worshippy :worshippy

So how does that work exactly?  Does that valve bleed off the vacuum signal when the engine is cold so the EGR valve doesn't open?  That filter probably rotted off within the first year.  That should be easy to make.  I don't remember the hose having a grean stripe on it though.