1973 351C-4V Engine Gauge Feed Wiring and Vacuum Hose Mystery

[jaredwinst]

Hi all, new to the forums so forgive me if this has been asked and answered in some way. I promise I looked through all the threads first! I inherited my father's 73 Mach 1, 351C-4V, 4sp manual, with A/C. The car is in good shape, but the engine needs a refresh (mice, too much time in a garage, etc).

I have a mystery I can't find an answer to in the 73 Ford Manuals, and wondering if/how my dad would have deleted this part (which I doubt since he was a stickler for keeping the car stock).

The Engine Gauge Feed Wiring Harness has a feed that is not connected, which I circled in the pic below.

Looking at every vacuum diagram I can find for this engine (which I think should be configuration 3-15A but the sticker is gone from the valve cover), I think they should go to an always open vacuum solenoid, which is not there.
The plot thickens, I cannot find a vacuum diagram anywhere that matches the current routing. Configuration 3-15A theoretically should be it, but it's not what I see.

On the spark side, all I see connected is a 3-port PVS and a dual-diaphragm distributor. Spark port to 3-port, 3-port branched to intake and front of distributor, 2nd port on distributor also goes to intake manifold. This does not match the 3-15A calibration.


On the EGR side, the UFO looking EGR valve on the spacer under the carb goes to a two-port temp-controlled valve connected to an H-shaped water hose connector, and then back to a vacuum tree on the back of the intake. The EGR port on the carb is capped.

Thoughts on what this wire is supposed to connect to, and if it might have ever been present on this car? And what vacuum line configuration I might have going on here for future reference?

Thanks in advance!!

 

[Hemikiller]

What's the build date on your car, and what's the DSO? There were several revisions of the emissions systems as the model year progressed, and California emissions cars were different than 49 state. Not all of those calibrations will be in the commonly available manuals, which are normally reprints of early releases. I have a 73 Emissions manual printed March 73 in the attic somewhere, really need to dig that out.

Those connectors are for the emissions solenoids as you suspect. Lots of things get monkeyed with over the years, so never assume that what appears original is truly "original".

 

[jaredwinst]

Here is a pic of the EGR side, with the H-shaped hose connector for the temp sensor (the hot and cold side of the heater hose to the cabin go through it). Thankfully this connector still seems to work, as I cannot find a replacement. Its pretty badly corroded. Does this part have a name?

 

[jaredwinst]

@Hemikiller Thanks for the reply!

It appears to be a January '73 build. Attached are some specs. Also, dad purchased this car in Iowa, and has lived in an Iowa garage all it's life

 

[ib4stangs]

Here's a 73 data plate decoder link and DSO 43 states "Rockford" (Illinois?)...

https://classicponycars.com/73data.html

 

[Moderator73]

Here is a pic of the EGR side, with the H-shaped hose connector for the temp sensor (the hot and cold side of the heater hose to the cabin go through it). Thankfully this connector still seems to work, as I cannot find a replacement. Its pretty badly corroded. Does this part have a name?

View attachment 85152

I have the same question about this H-shaped connector. I’ve been trying to find a replacement myself but having no luck. My 73 was a May build date so I guess one of the last ones. Here’s what mine looks like. I discovered its condition this summer when my heater core ruptured and I was putting a bypass on this connection to enjoy the car over the summer. Now I’m in the process of tearing out the heater box and restoring.

 

[Sheriff41]

I have the same question about this H-shaped connector. I’ve been trying to find a replacement myself but having no luck. My 73 was a May build date so I guess one of the last ones. Here’s what mine looks like. I discovered its condition this summer when my heater core ruptured and I was putting a bypass on this connection to enjoy the car over the summer. Now I’m in the process of tearing out the heater box and restoring.

View attachment 85186

Have you checked with a radiator repair shop to see if they can restore/replace the tubes?

Also: https://www.ebay.com/itm/1647885789...zVgBOgA1PrA6O/WcW1G5Kw0HE=|tkp:Bk9SR5KH8r6pYw

 

[Moderator73]

This is fantastic! Thanks so much for both suggestions. I’ll start with the ebay listing. I looked there already but had no idea what it was called so of course came up empty.

 

[Doug's 73 Mach1]

The two wire connectors go to a EGR cut out solenoid mounted on the driver side valve cover inboard front corner. The 73 wiring diagram shows the connections and the solenoid. 4 speeds for 73 also used another emissions related 3 port valve mount on the passenger side rear corner area on the intake manifold. I could not tell from the photos if that valve is there. Here is a photo of the 3 port valve.