84 SS Vacuum Lines, Where do they go?!?!?

[Supa.Slo.SS]

Hello everyone, I made a rookie mistake and did not note the location of every vacuum line on my 84 SS. It is all original with all the smog still on it. Below are (3) lines/openings I have not clue where they go. I found the smog emissions/vacuum line routings but no of these are seen.

1. On the back of carberator (Rochester) right below and towards the passenger side on the big line that goes to the brake booster there is a small nipple, what does that connect to? See picture.

2. On the back of the intake, there a threaded "nipple" with (2) outlets. The outlet going straight up I know goes down to the transmission, however the second outlet again no clue where it goes to. See picture.

3. From underneath the brake booster there is a bundle of wiring harness & out of that there is what looks like a vacuum line, again don't know where this goes. I think it's for the cruise control which I dont have but maybe someone can confirm.

Thanks in advance

 

[MrSony]

Not all ports are used. The empty ports listed are manifold vacuum sources if I recall correctly. They have vacuum at idle. A ported or timed vacuum source will not.

 

[CopperNick]

At least one of them is the vacuum source for the cabin HVAC, that is heating, ventilation, A/C. If you pull the heat control head out of the dash, you will likely find a whole nest of those vacuum lines. Another one is likely to be located in the T-stat housing. That is actually a vacuum switch that is fed continuous vacuum and, as the internal element absorbs heat it opens and closes the other ports and directs vacuum to and through them to various locations. There is another vacuum port that attaches to the snout on the stock air cleaner and operates the flapper valve in it. The ECU may also receive vacuum driven signals via devices known as VOES or vacuum operated electrical switches. Can't think of any others right now. Most of that rat's nest of vacuum plumbing had been disabled or turfed when I bought my '85 and I only replaced the minimum amount of it needed to operate the HVAC and distributor. Depending on where you live and what laws exist that govern smog and sniffer tests for older vehicles, plus how far towards stock you are planning to go, you might want to score a factory service manual and use it to figure out what goes where.

Nick

 

[MrSony]

I run my hvac vacuum source from that rear carb port to the two port vacuum ball with a one way check valve. Works great. Purple line goes to the small nipple on the ball.

 

[Clone TIE Pilot]

The small barb by the brake booster is for the vacuum sensor. On a 84, it will be a black box with 3 wires mounted on the passenger side wheel well.

 

[Supa.Slo.SS]

Thank you all for the replies!!