C4 Auto Vacuum Line

pyroman · Sep 26, 2009

I've got a vacuum line at the back of the engine running along the bell housing. I read somewhere that this line was important to make sure the transmission is shifting properly. I can't remember where I got this info, I spent all morning flipping through my shop manual trying to find out about it but failed. What I need to know is where it hooks up. If it helps, I have in dash a/c and it's a 67 that originally had 289.

Thanks

JC Mustang · Sep 26, 2009

There should be a "vacuum tree" screwed into the back of your intake manifold to which this connects. It's likely that your A/C is also connected to this.

pyroman · Sep 26, 2009

This is what you're talking about right?

Do you know what the other 'nipple' is for? Also I'm not going to use the A/C for now so I'm just got stick a pipe plug in where the A/C line goes.

Also, while on topic. What is this?

I'm thinking it's the vacuum reservoir, but it looks so much smaller than all the vacuum reservoirs I've seen for this car. Anyone know what its from?

Thanks

2+2GT · Sep 26, 2009

It's a later model maybe Japanese vacuum reservior. Your original was a steel can, which probably rusted so they stuck that in to keep the AC controls working.

JC Mustang · Sep 27, 2009

pyroman said:
This is what you're talking about right?

That's the one.

pyroman said:
Do you know what the other 'nipple' is for? Also I'm not going to use the A/C for now so I'm just got stick a pipe plug in where the A/C line goes.

Any extra nipples would be for any other accessories requiring vacuum. You can cap them if you don't need them.

pyroman · Sep 28, 2009

I was looking at a vacuum diagram and noticed the vacuum line running off the tree goes straight to the vacuum reservoir and not the transmission vaccum line. Also I had one picture of my old engine with the tree installed and you could see it clearly running to the vaccum reservoir. The other nipple has always been capped. Is there anywhere else it is supposed to attach?

2+2GT · Sep 28, 2009

pyroman said:
I was looking at a vacuum diagram and noticed the vacuum line running off the tree goes straight to the vacuum reservoir and not the transmission vaccum line. Also I had one picture of my old engine with the tree installed and you could see it clearly running to the vacuum reservoir. The other nipple has always been capped. Is there anywhere else it is supposed to attach?

The modulator on the back of the transmission should be attached directly to manifold vacuum, NOT any vacuum reservoir. A reservoir would interfere with proper reaction of the transmission to changes in the engine.

pyroman · Sep 28, 2009

Thats what I figured. I suppose I'll just hook it up to an appropriate vacuum source on the carb.

2+2GT · Sep 28, 2009

You'll be better off putting the brass vacuum fitting back on.

pyroman · Sep 28, 2009

I plan too because I need vacuum for my HVAC system. I suppose I could just run it off that capped nipple then.

C4 Auto Vacuum Line

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