Getting the vacuum systems hooked up was one of the more challenging and confusing aspects of the swap.  When I looked at the maze of vacuum lines in the donor car I was overwhelmed.

When you look at something like this, it's no wonder it can feel overwhelming.

The very first first thing that I did was label the vacuum lines on the chassis end and the connector on the engine side when I took the engine out. That way I would be able to match up the proper device and connection when it came time to put the system back together in the target car. You can see the little flags labeled V1, V2, V3 etc in the picture above. 

The second thing I did was was try to devise a system of labeling the lines and the devices in case something got separated when I brought things across to the new car. Here is my labeling system applied to a switchover valve. I used both color and number of dots to indicate which tube went where. (Note the same marking on the electrical connector too as a backup) 


I left everything intact in the donor car until it was time to bring things across. Then I unhooked everything as a unit and brought everything across at the same time, trying to keep the lines from separating.  I was then able to position the components in appropriate places on the drivers side firewall and mount them. I tried to keep things together as much as possible. Notice the simple aluminum mounting bracket I built for the EGR (vacuum converter and switchover valve) devices. 

The functional diagram for each year car will be invaluable of carefully reconnecting the entire vacuum system and getting it running properly.

For the main vacuum line between the vacuum pump and the brake booster, the original hard plastic line just won't work. A great alternative is standard 5/16 fuel line. It is very flexible and allows easy routing, and also won't get in the way as you work on the car on that side because it's so flexible. 

Vacuum Shutoff

I elected to go with a manual vacuum shutoff rather than try to fit the combination ignition switch/vacuum switch from the donor car. This was rather simple. I just grabbed a vacuum solenoid off of a car in the junk yard on one of the half price sale days, and used that. I teed into a convenient vacuum line and hooked the other end to the vacuum shutoff on the injector pump. A switch on the dash operates the solenoid and vacuum is applied to the shutoff. The problem with a simple vacuum solenoid, however, is that when it is disconnected it won't release vacuum, preventing the car from being started again until vacuum bleeds off, which could be a very long time. So I added a very tiny vacuum bleed in a plastic hard line going to the shutoff valve - small enough to not prevent full vacuum being applied, but large enough to bleed off 14" of vacuum in 3 seconds. Being this tiny, there is a great chance it could get plugged, so I rigged up a filter. 

Here is my "filter". I wrapped a couple of inches of shop towel around the plastic line covering the vent and then slid a length of appropriate diameter heat shrink over it and then shrunk just one end to hold it in place. It's well protected so it should last many years. 

Here's a little vacuum tip. My SL has an "economy" gauge in the cluster, which is really just a vacuum gauge. The more throttle on a gas engine, the lower the vacuum, so max economy comes when the vacuum is the highest. By hooking up the vacuum gauge to the vacuum system, this becomes an early warning system for vacuum problems. (And it will also prevent the engine from being shut down if it is not connected as can happen in working in and around the cluster)