Engine Vacuum line routing '81 CJ7 4.2L

[Nikwho]

Hello all, I've been searching old threads and trying to find my answer that way, but not finding exactly what I need.

I just acquired my '81 AMC CJ7 yesterday. It has sat for 4 or 5 months, and 6 months prior to being moved then. I want to freshen it up a bit.

My main question is regarding the vacuum lines. I have a line coming off of the carb, with a few inches of line, then a tee fitting. I'm not sure where that line goes. I'm going to replace the fuel filter and verify that the return lino the tank is clear.

What do these rigs need vacuum provided to? I figured that I could buy a few rubber vacuum caps, bypass mostly anything that has a vacuum hose hooked to it, and run a vacuum line from the carb, to a PCV valve in the valve cover.

Anyway. Im happy that I found this forum! Now, Im off to NAPA to buy a fuel filter, 25-ish feet if fuel line, two engine mounts, a Transmission mount, an oil filter and some oil. Gonna get this rig freshened up, and start driving it.

 

[Nikwho]

Okay, I figured out the routing by the carb. I moved the longer piece up, closer to the air filter base plate. Then connected it to the tee fitting. That seems pretty obvious how that connects. But, then, where is that line supposed to run to? It just hangs down and is not connected to anything. Then, the hose that connects below and behind the carb (manifold vacuum) is connected to the pcv valve atop the valve cover, which has a tee, with one end capped. It would make no sense to tie the first vacuum line to that tee, as it's redundant and unnecessary. The intake plenum pulls plenty of vacuum to alleviate any crankcase pressure issues. Considering where the connection points, I assume that the two lines that connect higher (at LEAST the far upper one) is a ported vacumm source. So, that would tell me that it may be for vacuum advance. This rig doesn't have vacuum advance. Does anything else on it require a ported vacuum source?

No Transmission modulator, as it is a standard transmission. No vacuum advance. I cannot think of anything, sans smog equipment, that would require such vacuum. I'm thinking that I will cap the two ports near the top of the carb. This thing should run better without a vacuum leak.

Oh, I need to go check where the brakes are sourcing their vacuum...

 

[TSB8C]

Here's a great resource for vacuum line routing (for those keeping such). Web Site Link

And could check here as well: Local Link

 

[Armyvet25]

yeah it all depends on your current engine year and setup, many emission related poo poo lines lol.
Me it's a Brake booster vacuum and maybe a advance to the distributor if required and that's it. Sometimes I'll add an aftermarket fuel eco gauge which runs on vacuum, keeps me from being heavy footed.
Also your heater/vent blend doors may require them if not cable controlled.