I am finished with my resto of my '78 F-150 (except for paint) but the ported vacuum switch on the Edlebrock manifold (motor is a 460...all power and fac air and C6) is a real puzzle. When I got the truck 2 1/2 years ago and started on the resto...many of the vacuum lines were not connected to anything. There was a 4 port switch on the back of the intake manifold. The top port is now connected to the power brake master cylinder. The single port on the driver's side of the switch is now routed to a metal line that goes to the transmission. The top port on the passenger side of the switch is connected to the cylindrical shaped vaccum canister on the fender well. The bottom port on the switch is plugged...not connected to anything as it was when I got the truck. I do not know if this model truck came from the factory with a 4 port switch...or a 3 port...or... It bothers me that one port is simply plugged. All the vacuum switches seem to work...the air conditioning system works...even though it does not blow very much even at a high fan speed...and the power brakes work.
I am just not certain that we have corrrectly routed the hoses from the ported vacuum switch...and have been unable to find drawings in either a Chilton repair book or similar ones...no one seems to show diagrams of ported vaccum switches and how the hoses should be routed. I keep looking for someone with a similar truck and motor here but so far...have not run into that person.
Anyone have any ideas about whether we are ok with our installation of these vacuum lines...or do we need to do some more work here?

 

What you're seeing is not a ported vacuum switch, it is actually a "vacuum tree" - it simply provides a way to hook up multiple lines to manifold vacuum. Brake booster, heater controls, transmission modulator are all common things that tee off of this thing. Any available ports that aren't needed just get plugged.

A ported vacuum switch is something that plugs into a water jacket that opens and closes based on coolant temperature. The thing you are seeing isn't any sort of switch - it's just an "expander" and all the connections on it are powered all the time.

 

Try this

linky 1


or


linky 2

 

Thanks so much for the replies.
I need to put a vaccum guage (or my finger) on each line from this vaccum tree (it is old and rusty) to make sure they have vaccum and that this old part is working...and if so, I guess it really does not matter which line goes where if they are all common lines coming from this tree, right? I am assuming they would all have the same pressure.
I am wondering if Ford would have put a 4 line vaccum tree on from the factory if one line ended up being plugged? Since the truck has factory air...power brakes...and the C6...these three lines would surely have been installed when the truck was new...but I still cannot figure where the fourth line would have gone...

 

Thanks for the illustrated pics. I will try to print them off and make them darker as they are pretty dim. Hopefully, I can see some of the vaccum lines routed on those pics. I appreciate the replies.

 

You are correct.

Yes, they would have. With any sort of manufacturing, old Ford trucks included, it is cheaper to use the same part across the board rather than having one part number for trucks that only need to feed 2 vacuum lines, another part for 3 vacuum lines, another for 4, and so on. Another reason is expandability. An extra port gives the owner the ability to easily add another vacuum line if needed. Every old Ford I have ever owned has had at least one extra vacuum tap that is plugged. You will find there are cases like this all over your truck. For example, there are various items throughout the wiring harness that have connectors for things even if you don't have them. The same reasoning applies - it's cheaper to use the same wiring harnesses rather than a different one for each set of options.

 

You can see a "general" illustration of the 4 way vacuum tree in the two links, but there's no ID number pointing to it. The one that's illustrated may/may not be correct for the vehicle.

If someone here has the 1973/79 Ford Light Truck Parts Catalog on a CD...look in the TEXT under basic part number 9A474 (Section 93 / Page 45). On this page are not only all the part numbers of the various types of vacuum trees, but illustrations of them, too.

There's more than one type of 4 way tree...it depends on the year, what size the engine is, and whether the vehicle was originally sold new in CA.

I can't scan and post the illustration, because I'm using the above Ford truck parts catalog on microfiche.

 

More thanks to everybody who replied.
What a great resource this website is.
I have learned so much these last couple of years restoring this old truck...can't wait until I start on the next one.
Thanks again.

 

Like this Bill?

 

That's the one..thanks for posting the illustration.

The CD version of the parts catalog is off a page because of the catalog dates. The CD is, I believe dated 1979, my microfiche slides are dated 10/88.

 

WOW there were a lot of different types of these vaccum trees...and the one on this truck is different from all of these...as I thought it might be. It is similarly shaped to the one shown for 1974 but has two additional ports on the side.
I suspect the previous owner put whatever he could find on the intake manifold that would 'sorta' work as he did with most everything else when he decided to sell the truck three years ago. I have replaced burned wires...disconnected wires...hoses that go no where...and a thousand other mysterious things that were done before I got the truck. Not unusual I know but certainly not mechanically correct.
I think I will try to find a new replacement 4 port vaccum tree from Blue Oval or LMC or a parts store...and take this old rusty one off.
Thanks for those pictures.

 

yours is probably like this.
I found this on another post.

this mi1llion guys has lots of pics and illustrations.

 

When I began to pull the truck apart two years ago to repair the mess that was a part of all the systems on it...I found things that were so much worse than anything I see in that picutre.
I did check the vacuum tree today...and the four ports on it all have good vacuum...so I guess it is working and is connected properly. That is a first but a welcome one.
Thanks again to everybody who provided help and information.