Questions?

7173Mustangs.com

Help Support 7173Mustangs.com:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
The one that runs down to the steel tube is the one that runs to the vacuum modulator. As long as the one that runs under the carburetor is connected to an intake manifold vacuum source that should be fine. Except, for the open port on the firewall mounted vacuum manifold. As long as that port is open none of the attached devices will function properly. It needs to be capped. It will also affect carburetor tuning and distributor advance.
 
Don C said:
The one that runs down to the steel tube is the one that runs to the vacuum modulator. As long as the one that runs under the carburetor is connected to an intake manifold vacuum source that should be fine. Except, for the open port on the firewall mounted vacuum manifold. As long as that port is open none of the attached devices will function properly. It needs to be capped. It will also affect carburetor tuning and distributor advance.
Click to expand...
So should I plug it and see what happens? I'm not sure where the first hose goes but it shares a air chamber with the T line. The third line runs to the other steel tube to the transmission and shares the air chamber with the open port. Is this correct? Just want to make sure that something isn't hooked up wrong. And any idea what the open port is supposed to connect to? Side note I need to find a mechanic. Lol
 
A bit of history - the 1973 cars were the first year for EGR. Ford used a "dual area" vacuum modulator on their automatics to raise the shift points when the EGR was active - hence the four place vacuum tree on the firewall and the two steel lines running down to the modulator. See the vacuum diagram below. The larger of the two steel lines is the signal to the modulator for shift timing. It should have a full manifold vacuum source. Your EGR system has been removed, so there's no need for the second vacuum line.

You have an AC car, it's just missing all the underhood components.

The vacuum line that is coming off the manifold vacuum nipple on the carb, is that the same one that is Tee'd into the transmission vacuum line (marked as A)? Where does the line coming off the firewall manifold go (marked B)? The modulator needs a solid vacuum source at all times. If the B line is open to the atmosphere, that will absolutely cause shifting issues.

1723210045368.png




1723209370094.png



1723209479436.png
 
It appears the vacuum line on the right front of the base of your carburetor is routed to possibly an open end on the air cleaner base. Can't tell without lifting the air cleaner.
Also it looks like that carburetor has experienced some backfires, resulting in the sooty black appearance.
 
Hemikiller said:
A bit of history - the 1973 cars were the first year for EGR. Ford used a "dual area" vacuum modulator on their automatics to raise the shift points when the EGR was active - hence the four place vacuum tree on the firewall and the two steel lines running down to the modulator. See the vacuum diagram below. The larger of the two steel lines is the signal to the modulator for shift timing. It should have a full manifold vacuum source. Your EGR system has been removed, so there's no need for the second vacuum line.

You have an AC car, it's just missing all the underhood components.

The vacuum line that is coming off the manifold vacuum nipple on the carb, is that the same one that is Tee'd into the transmission vacuum line (marked as A)? Where does the line coming off the firewall manifold go (marked B)? The modulator needs a solid vacuum source at all times. If the B line is open to the atmosphere, that will absolutely cause shifting issues.

View attachment 91799




View attachment 91797



View attachment 91798
Click to expand...
Yes hose A runs to under the carb I'm assuming to the manifold. Haven't traced hose B down to a connection yet. I've had the car for a week. But have been out of town aside from a few quick trips back home. I need to get a good solid set of jack stands so I can get it up and get a better look underneath. I currently have Harbor Freight jack stands and they may be the ones that were recalled for failure. So not willing to chance it with their jack stands either way.
 
Don C said:
Those are heater hoses. What you need to look for is more of the small hoses that you can see above the heater hose on the right. There should be one that runs from a "vacuum tree" on the back of the intake manifold to the rear of the engine and then follow the bellhousing down to under the car, that would supply vacuum to a vacuum modulator (called a vacuum diaphragm in the service manual) on the right side of the transmission.
Click to expand...
The rectangle aluminum block to the left of the heater hoses is the air conditioning expansion valve which should be sealed up until you reconnect the rest of the AC system. When you go cruising in the summer the air conditioning feels great.
 
Bill Kanode said:
The rectangle aluminum block to the left of the heater hoses is the air conditioning expansion valve which should be sealed up until you reconnect the rest of the AC system. When you go cruising in the summer the air conditioning feels great.
Click to expand...
Yeah it had AC at some point. I think the previous owner said it had gone out and he couldn't find a replacement unit for it. I'm big fat guy so AC is kinda important, but if it's not being driven daily and just coming out to go to cruise ins and stuff I'm not gonna put it at the top of the priority list.
 
Update. Finally got an opportunity to take her out and run. She does in fact have all 3 gears (seller told me 2). I think maybe her didn't realize it because it shifts so smooth from 2nd to 3rd that I could barely notice it myself. I was babying it home the night I got it due to a combination of air shocks clunk and poor dash illumination. So probably why I didn't notice it shifting either.
 

Similar threads

C
Recommendations to upgrade 72 vert
Replies
8
Views
611
will e
W
F
Wheel Pro's needed
Replies
1
Views
550
Don C
Don C
V
FMX Transmission dipstick question
Replies
4
Views
544
vintageman
V
andy72
351C IDLE SPEED PROBLEM, FMX CLUNK?
2
Replies
32
Views
5K
AcesArneson
AcesArneson
Ronk
Vehicles For Sale 1973 Mustang Grande w/351 Cleveland 4bbl up for sale
Replies
0
Views
1K
Ronk
Ronk

Latest posts

Back
Top