Manifold Vacuum Tree

7173Mustangs.com

Help Support 7173Mustangs.com:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

GeoBW

Well-known member
Joined
Sep 16, 2017
Messages
75
Reaction score
1
Location
Australia
My Car
1973 Mach 1 - matching numbers, 25,000 miles Eleanor look-a-like
[url=https://ibb.co/mvrntk][img]https://preview.ibb.co/bG8YYk/1_lr.jpg[/img][/url]

[url=https://ibb.co/dwgntk][img]https://preview.ibb.co/fEZ7tk/2.jpg[/img][/url]

[url=https://imgbb.com/]picture hosting websites free[/url]
Can anyone tell me where the 4 points on the tree - see attached - connect to? Pulled this '73 Mach 1 apart 3 years ago and did not photograph this. There needs to be some connection to the FMX transmission in the lower circle.

Did search but could not find another thread on this. If I missed it please direct me to it. Thinking the larger top connector goes to the power brakes?
 

Attachments

  • Manifold.jpg
    Manifold.jpg
    1.8 MB · Views: 1
The large port on the manifold tree is for power brakes. The dual steel line unit is the 73-only dual area auto trans modulator vacuum lines. Hook full manifold vacuum to the larger of the two, and that should connect to the rear nipple on the modulator. You don't need the other line, as it was used to raise shift points when the EGR system was active - which you obviously have eliminated.
 
The large port on the manifold tree is for power brakes. The dual steel line unit is the 73-only dual area auto trans modulator vacuum lines. Hook full manifold vacuum to the larger of the two, and that should connect to the rear nipple on the modulator. You don't need the other line, as it was used to raise shift points when the EGR system was active - which you obviously have eliminated.
Thanks @Hemikiller. Just to clarify: large top port to brake booster: tick. Not sure if we eliminated the EGR - where does it normally take off from, or was it lost with the extractors? I presume it takes one of the 2 'medium' size ports? The remaining two ports are one 'medium' size and one small one which match the two from the FMX transmission modulator?
 
Thanks @Hemikiller. Just to clarify: large top port to brake booster: tick. Not sure if we eliminated the EGR - where does it normally take off from, or was it lost with the extractors? I presume it takes one of the 2 'medium' size ports? The remaining two ports are one 'medium' size and one small one which match the two from the FMX transmission modulator?
EGR on a 351c was handled internally through the intake, and had a spacer under the carb with the valve attached. Since you're using an aftermarket intake, the EGR capability is gone.

The rearmost port on the FMX modulator needs full manifold vacuum. Whichever of the steel tubes feeds that port is the one you'll use, which IIRC is the larger of the two. You don't need to hook up the forward port on the modulator as that was switched through the EGR system, not direct to manifold vacuum.

The remaining ports will be used or blocked off, depending on what original accessories you're using. AC would use one port to the vacuum reservoir on the RH fender apron. Factory air cleaner would need a vacuum supply for the flapper door.


1672667250205.png
 
Looks like you're taken care of by the others. Here's another link for your reference: https://7173mustangs.com/threads/vacuum-hose-diagrams.23844/
Thanks Sheriff, this link takes me to a post which applies to my car i.e.
"Hi ... these diagrams are great except they don't show my car ... 73 351 C 2v they show a 4V ...any suggestions ..."
and the link in response i.e. http://www.mustangbarn.com/1973-engine-vacuum-diagrams.html
no longer works/

Does anyone have the diagram for the 351 C 2v?
If not I can work from @Hemikiller's great help.
 
Hi George
The attached vacuum hose diagram might help.
Cheers Frank
I normally refer to the engine vacuum schematics from the Forel Publications Shop Manual, Volume 6, which has excellent diagrams. They do not include the vacuum calibrations for the 351 4v engines for 1973, but I came across those from another source, and added the to my Forel PDF (after I removed their silly little copy-protection password). I have not looked through the PDF offered by Vicus (yet) as I in the midst of another project. But, just in case his PDF is also missing the two 1973 351C 4v vacuum calibrations I have included them in this post. The calibrations are 3-15A and 3-16A.
 

Attachments

  • 1973Mustang_351-4v-AutoTrans_EngineVacuumCalibration-Annotated_20220329.pdf
    398.8 KB · Views: 0
If the Mustang Barn 2351C 2v calibrations do not match what your engine calibration is, or just does not look "right," let me know and I will provide the Forel 351 2v calibrations I have from Shop Manual 1973 Mustang Volume 6 (emission control and vacuum calibrations). If you are interested in getting the Forel Shop Manual (single PDF file, but it includes all the emission control and engine vacuum routing diagrams other than 351 4V [I added that from a different source], you can get if for a very reasonable price at the following link:

https://www.forelpublishing.com/clickbank/index.html#1973

Until 1973 the Shop Manuals I have come across have had either inadequate or no information on engine vacuum schematics, to include when I used to work at a Ford dealership in SoCal. It is almost like Ford had not taken the need for that information very seriously or something, art least until the 1973 manuals came out. That is why I am so glad I came across the schematics from Mustang barn for 1967 - 1972, (with their permission) consolidated all of the 67-72 vacuum diagrams into a single PDF file grouped and sorted by year and engine size. That consolidated file is attached for anyone who might need it. No fee from e or Mustang Barn, of course.
 

Attachments

  • _1967-1972_Mustang_EmissionControlVacuumSchematics_ConsolidatedGroupedAndSortedByYear__20211003.pdf
    15.2 MB · Views: 1
Back
Top