Questions?

Don C · Aug 8, 2024

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.

Ehenry77 · Aug 8, 2024

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.

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

Don C · Aug 8, 2024

The open port may be for the vacuum switch for air conditioning

Ehenry77 · Aug 8, 2024

Don C said:
The open port may be for the vacuum switch for air conditioning

Yeah I was wondering if it had to do with AC since the car doesn't have it.

Hemikiller · Aug 9, 2024

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.

RacerX · Aug 9, 2024

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.

Ehenry77 · Aug 9, 2024

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

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.

Bill Kanode · Aug 9, 2024

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.

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.

Ehenry77 · Aug 10, 2024

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.

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.

Ehenry77 · Aug 17, 2024

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.

Questions?

Help Support 7173Mustangs.com:

Don C

Fords Forever

Ehenry77

Active member

Don C

Fords Forever

Ehenry77

Active member

Hemikiller

Well-known member

RacerX

Well-known member

Ehenry77

Active member

Bill Kanode

Well-known member

Ehenry77

Active member

Ehenry77

Active member

Similar threads

Latest posts

Questions?

Help Support 7173Mustangs.com:

Fords Forever

Active member

Fords Forever

Active member

Well-known member

Well-known member

Active member

Well-known member

Active member

Active member

Similar threads

Join the conversation!

Join today and get all the highlights of this community direct to your inbox. It's FREE!