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Discussion Starter #1
Hey All,

I'm putting a 66 coupe back together. It sat in a barn for 25 years, the engine and drive line more or less dismantled. I've made good progress, but have run into a problem with what I THINK MIGHT BE the vacuum modulator line. It appears to have been crimped at some point in the past. Here's a picture:

748066


Here are my questions:
  • First off, any way to tell if this is actually the hard line for the vacuum modulator? It had a 5/16 hose on the other end and a clip about 1/3 of the way up.
  • Second, if it is the right line, any idea why it might have been crimped like this? Is that normal?
  • Third, if it isn't the right line, I'll just order a pre-bent line from ClassTubes. One problem. I have a 66 car, but a C4 transmission out of a 73 Maverick. I'm guessing I'd need to be this line. Sound right?
I really appreciate your help. You guys are awesome. I've learned so much on this forum that it is ridiculous!

Chris
 

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Hey All,

I'm putting a 66 coupe back together. It sat in a barn for 25 years, the engine and drive line more or less dismantled. I've made good progress, but have run into a problem with what I THINK MIGHT BE the vacuum modulator line. It appears to have been crimped at some point in the past. Here's a picture:

View attachment 748066

Here are my questions:
  • First off, any way to tell if this is actually the hard line for the vacuum modulator? It had a 5/16 hose on the other end and a clip about 1/3 of the way up.
  • Second, if it is the right line, any idea why it might have been crimped like this? Is that normal?
  • Third, if it isn't the right line, I'll just order a pre-bent line from ClassTubes. One problem. I have a 66 car, but a C4 transmission out of a 73 Maverick. I'm guessing I'd need to be this line. Sound right?
I really appreciate your help. You guys are awesome. I've learned so much on this forum that it is ridiculous!

Chris
Yep that could be the modulator line. If you are still using the stock carb/intake get the line for your year, otherwise you can either make your own line or modify the end to fit your carb/intake. You should have a short rubber line on the modulator.
 

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My C4 is not in a available to inspect, but my FMX has slip connections at either end of the tube w/o the threaded fitting.
 

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Vacuum modulator lines only have a rubber connection at the ends, not a flare nut. That's probably an old transmission cooler line being that it's 5/16". You might want to order a set of cooler lines while you're at it.

The line you linked you will work fine. Technically, it's wrong for a 73 C-4 since they originally had a dual area modulator that raised shift points when the EGR system was activated.
 

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+ 1 on that being a cooler line and fitting that would go into either the radiator or the side of the tranny... there are 2 lines you'll need for that. For the vac mod, I had a C4 from 2004 til 2015 that ran just fine with only a rubber line from a vacuum tree on the back of the intake down to the modulator.
Just a word of caution: there's a pin in the tranny side of the modulator. Don't lose it. You'll never get it out of 2nd.
 
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Its twisted like that because the nut seized to the lubing. When the person broke the nut loose from the fitting that it was screwed into the tubing kept twisting with each rotation of the nut instead of the nut spinning loose on the tubing. That's quite a butcher job. It probably Is a cooler line from the trans to the radiator. It would be a lot longer than a trans vacuum modulator tubing.

Install a manual trans and you won't have to worry about it.

If you look at that nicely formed 180 degree loop, it looks like the one on the line on this reproduction. I was looking they make them in steel or stainless. Because shipping has gotten so expensive it adds a lot to the cost of a Mustang build. If you have a nearby automotive swap meet with vendors that sell Mustangs parts call them up and have them bring the parts you need to the swap meet or wait to bundle a bunch of parts together to be shipped at the same time.

1966 Ford Mustang V8 C4 5/16
 

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Discussion Starter #11
You guys are awesome. You're right: I crawled under the car and tested and this is definitely a transmission cooling line. I guess I'll be ordering a new set of those! I must have the vacuum modulator line somewhere then, so I'll take a look again and, if I can't find it, I may take you up on your offer, BW66.

Again, thanks so much for offering your expertise. This forum is an amazing resource, and it is only because you are all so willing to help a newbie like myself!

Chris
 
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