Okay--I've been working on my truck for almost a year and have a few little things to clear up. I'll use pics to help:
PIC 1

Removed this during the build and never hooked it back up. There is a vac line going to the transmission on the passenger side that is hooked up. I believe this does as well--goes to tranny, that is. The little mounting plate bolted on to the transmission housing. Anyone know what it is? Another vac line? It goes on the driver side.
PIC 2

This line comes off of the passenger side exhaust manifold. It is directly behind the heat stove pipe for the auto choke. What is supposed to connect to it?
PIC 3

Not actually from my truck (the pic), but I didn't feel like getting under there tonight. The heat riser has an opening that looks like a vacuum attachment. It was not hooked up to anything before I took out the engine. I am being lazy right now as I'm sure my manual covers this, but I thought I'd just ask what type of connection applies here. I mean, what is attached to the nipple on the canister? Other pics I found show the same type of bimetallic spring that the auto choke uses to open this valve.

It may help to know that I had CA emission equipment on the truck that I removed: smog pump and lines, emissions rails that hooked into the exhaust manifold...
I thought that perhaps the heat riser was connected to one of those rails, but I can't remember.

Thanks for your help in advance.
Tyler

 

Good job on the pics, but what are the specs on your rig? About all I can tell is you have an FE with an automatic. And since it has all that emissions stuff,I can't help you there. I have never seen it before, I live in a free state...

 

Specs-
390
C6
2wd
I removed the thermotrac. I just don't know what that tube off the exhaust is for.

 

It was probably plumed into the cab heater, CA's attempt at population control....

... Sorry for razzin you man. The only thing I have seen a tube that size coming of the exhaust was an EGR system on my '88
. We did have a grain truck witha 390 that had 2 smaller (3/16) or so tubes for the choke stove, but those came off the exhaust manifolds

 

All automatic transmissions run manifold vacuum to the modulator behind the pan. Various smog motors also have a second vacuum signal that runs to the modulator, often the same ported source running to the EGR valve. This was used to help maintain the signal level at the modulator when the EGR valve opened.

That looks like the fresh-air intake to the hot-air choke stove.

 

X2. Some C6's had a dual diaphragm modulator. One line went to manifold vacuum, the second went through some monkey motion to do basically the same thing. By now, most of them have been converted to the single line diaphragm.
That second line goes to just below the air horn on the carb. At the back of the carb there should be a nipple that goes up into the air horn, that's where this line hooks to. Its so the automatic choke draws filtered air into it.
Starting in '75 the heat riser was vacuum operated, earlier models used a thermostatic spring to work the valve. I know the vacuum line goes through a ported vacuum switch but other than that, I'm not too sure how the line is routed.

 

Thanks all. That does help. I think I'm good on the PICS 2 and 3. Do I need to hook the tranny line to a vac source?--the truck is operating without it currently.

I picked up a few ported vacuum switches today and found some diagrams in my manual, so I will get those lines tied in.

Just to be absolutely sure, the metal line in pic 2 goes to the air horn on the carb, right?

 

Since I'm at it, I'll ask one more vac question:

What should be connected here (port with red oval around it)? This is not the choke pull off port that is pointed out by the black arrow.

I currently have the port in question capped.

FMC, I've read a couple of your carb posts, pretty awesome. I was hoping you or Mike would know this.

Thanks.

 

Tyler, first, your C6 does need to be hooked up to a vacuum source. If you have a single diaphragm modulator, hook it up to full manifold vacuum. If you have a dual diaphragm modulator get rid of it and switch to the single line variety. The dual diaphragm version has two vacuum ports, one on the end like normal and a second one on the side.
Next. No, that's not the vacuum port you hook the line to. This line will go off at an angle from the carb pointed down and at an angle.
I'll see if I can find a picture. The line is actually on the bottom side of the cover, not in the body of the carb.

 

The yellow arrow points to the proper connection.

 

I got that connection. I meant PIC 2 from my OP; sorry if i wasn't clear. I was wondering what went to the port I circled in my pic (my 4th post of the thread). It's just capped.