1968 Carburetor Questions

[Jester]

Hi,

It's been some time since I last checked in here. And between then and now my oldest kid has turned 14 and decided to rip our C-code engine apart and install a new performer intake and an Edelbrock 500 Cfm carburetor (1404). Its all good learnings and he is on his way becoming a decent mechanic. Problem is he is not fully there yet, and I am certainly not one and quite limited in guiding him. So when it came to installing the carburetor we faced a few question marks I hope you might help me sort out:

1. There are 2 distributer hose connections on the new carburetor. It says one is for timed vacuum/emission controlled engines and the other is for manifold vacuum/Non emission control. Which should I use? As I understand it our engine should use manifold vacuum?

2. The new carb has a PCV port, which the old didn't have, but that one had a hose fitting on a spacer which I guess was a PCV connection? Does this engine have PCV? and can I assume I can to plug the hose that used to go into the spacer into the PCV port on the new carburetor?

3. Now to my biggest confusion: PCV is an emission control thingy isn't it? so how does this make sense if I should connect the distributor hose to Manifold vacuum/non emission control in #1?

4. What the heck does that hose marked with a red circle in the photo do? The only port on the carburetor it fits with is the Power brake port, but my car doesn't have power brakes.

Thanks for all support!

 

[rvrtrash]

Rob would be the expert here, but I'll chime in and then he can correct me if needed. :grin:

1) There are two ports because some cars use a dual diaphragm vacuum advance unit. Yours is a single advance so you would use the carburetor (timed) vacuum.
2) The engine does have PCV, and it did go to the spacer. You can use either and plug the other.
3) PCV (Positive Crankcase Ventilation) is emission control only in that it replaces the old vent pipe that dropped down by the transmission. Now instead of those oil fumes being vented to the atmosphere, they're reburned in the engine.
4) If you have an auto transmission, the hose probably goes to the shift modulator. That would get manifold vacuum.

Steve

 

[CougarCJ]

On #4 I think that is the line going to the choke. Insulated hard line from the exhaust manifold?

 

[rvrtrash]

Scott, I think you're right. I didn't look close enough.
Steve

 

[Jester]

Thanks! This answers 1-3 for me. But I am not sure I understand #4. This hose was connected to the stock carburetor. See picture. So I assume it has to attach somewhere to the new carb. But the only connection left is something called power brake port on the new carb which confuses me as my car doesn't have power breaks. Shall I just attach it to that port and be happy or have I got a Carb that is not fitting my car???

 

[robert campbell]

The Edelbrock carb has an electric choke vice the “heat tube divorce choke” on your stock carb. Your stock carb used the heat tube shown with a small amount of vacuum to draw the heat off the exhaust manifold to open the choke.

Your new carb uses an electric choke. A “keyed” 12 volt wire that is only energized when the key is in the “run” position only must be supplied to it. It use a heated disc to heat up the bimetallic spring to release the choke. The best place I find it is the 4 prong plug that goes to your auto transmission. There is a wire that is energized only in the run position.

The Edelbrock carb has a port on the front for vacuum to the PCV valve. Or if you use a stock 4 barrel spacer plate, it has a fitting like your old 2 barrel spacer plate. As steve said you can use either. And the Edelbrock carb has a port on the back of the carb that many people use for power brakes. You can use anyone of these ports for PCV as long as the others are plugged.

I notice you have a “dual diaphragm” vacuum advance, but the port closest to the dizzy is plugged. That is what I do, but better yet is to install a single diaphragm vacuum advance.

Distributor Vacuum Advance ECH VC970 | Buy Online - NAPA Auto Parts (napaonline.com)

You need to check your timing before installation and hen reset it after to the same initial timing. This vacuum advance is adjustable and I can help you with that.

I have notice you have not asked about carb linkage yet? That can be a little tricky. Some how I think this tread will get bigger as we help you.

Rob

 

[rvrtrash]

I notice you have a “dual diaphragm” vacuum advance, but the port closest to the dizzy is plugged. That is what I do, but better yet is to install a single diaphragm vacuum advance.

Rob

I need to get new glasses or a better monitor. I didn't catch the plugged vacuum port.

 

[1968Cally]

Good guidance for you from previous answers. I notice you have a new looking chrome thermostat outlet. Those are notoriously of low quality and prone to leaking. You may want to use the old housing after cleaning it up and painting it to match the intake manifold.

 

[Jester]

I am beginning to think you are right Rob. It might be a long thread. So before continuing, I just want to say I REALLY appreciate the help!! And here comes a few more questions:

1. When it comes to the single vs dual vacuum advance I understand you as I CAN run it as is but its better to shift to single. Correct? If that is right, then I think we will put that on the back burner for now or I will never get this car running again...

2.The new carb I have is an Edelbrock 1404. It does not have electric choke: https://www.edelbrock.com/performer...-with-manual-choke-in-satin-non-egr-1404.html. I guess this leads to a whole set of new questions, but starting with the most important ones: as the stock set up is activating the choke with the gas pedal and the heat tube I wonder if I can make the set up work with this new carb or I should get another one? To get it working with the manual choke i guess I must install a cable through the firewall. When I allowed my boy to start doing this upgrade I talked to a mechanic who helped us get the parts and he said it was just a bolt off/bolt on job. Seems to be a bigger deal now... If it works with this carb and installing a manual cable is not a big thing(?), then I am back to the question what I shall do with the heat tube. Just plug it?

3. All the linkage questions are yet to come. I can only hold one thought at the time in my head so for now I just want to know if to get another carb and what to do with the heat tube and choke.

Thanks!

 

[robert campbell]

First +1 to Dave on that chrome Thermo housing. They make great paper weights!!

We can do the vacuum advance later. In this day and age, a manual choke is old thinking. I should have noticed. Might need a bigger monitor and better glasses also!

It a simple as a universal choke cable that you can attach under the lip of the dash of the car. You may be able to find an existing hole or need to drill one.
If you drill one, drill as close to the center of the car firewall and mount the choke near your fog light switch. This will put less cramped curves in the cable, and it will work smoother. I would not buy a cheap repop and here is a link to a factory Ford copy for Boss 302 and other high-performance Mustangs. It will look very nice next to the fog light switch. I will help you adjust it when that time comes.

https://secure.cougarpartscatalog.c...-mercury-cougar-/-1969-1970-ford-mustang.html

If this was my car I would put on a carb with an electric choke. They are easy to set up and work great. Your choice of the 500 CFM car is spot on. Not sure if you can return yours or not? Or sell it?

Below is a link to the electric choke version:

https://www.summitracing.com/parts/edl-1403

We will talke soon I bet!!

Rob

 

[1968Cally]

I have the 1403 on my J-code with a Shelby intake, K code style exhaust manifolds and a mild cam. Single diaphragm distributor using manifold vacuum. Works great! Easy to tune and never a hesitation or stumble.

As far as I can recall the electric versus the manual choke is the only difference in the 1403/1404.

 

[Jester]

OK. The Thermo housing needs to go it seems. I will reuse the original then. Check. I shall also ponder on the electric vs manual choke choice. Thanks. If you allow me to return to the question of the heat tube for the stock pedal choke: What have you done with it when upgrading? Did you just plug it and let it be? If that is an option, I'd like to do that and tie it to the hose pack next to it. I want it to be easy to restore to stock when my son is done with the car.

 

[1968Cally]

OK. The Thermo housing needs to go it seems. I will reuse the original then. Check. I shall also ponder on the electric vs manual choke choice. Thanks. If you allow me to return to the question of the heat tube for the stock pedal choke: What have you done with it when upgrading? Did you just plug it and let it be? If that is an option, I'd like to do that and tie it to the hose pack next to it. I want it to be easy to restore to stock when my son is done with the car.

You can just pull the heat tube out of the exhaust manifold -maybe. It very well might be rusted in the manifold. Could try some penetrating oil for a couple of days if that is the case. If that does not free it, break or cut it off at the manifold.

As far as plugging the hole, when I was a kid, I found just the right sized fine threaded bolt that I just was able to screw a little ways into the hole in the manifold to plug it up. Not the best way to do it. Others may know of much better ways without resorting to welding it. Maybe JB weld or something similar as long as it can stand up to the heat?

 

[franklinair]

In the "olden days" the exhaust thermal tube to the carb choke was called a "choke stove".

I have opted for Edelbrock, electric choke carbs as replacements.
I removed the tube completely and just plugged the hole in the exhaust manifold.
The +12 volts for the electric choke can be wired from the alternator output to the choke
(which only has power when the engine is running).
The choke Ground can be grounded at the carb base stud.

Neil

 

[Jester]

Allright! I think I have all hoses hooked up where they should and the other inlets/outlets plugged. If anyone is into Quality Control feel free to have a look as I am only about 70% sure I got it right. (C-code. No powerbrakes or emission control) I have plugged the forward facing PCV port on the carburetor and hooked the hose that went to the pcv inlet on the stock spacer directly to the intake manifold instead. Hope this is right. Or is it better to do it the opposite way around?

Given my set up is OK, I now move on to my next headache: Linkage!! How do I link the gas linkage to the carb the best way? Can I use the stock linkage or do I have to modify or order replacement kits? Remember, I am a non-voluntary newbie to this, trying to support my 15 year old son so please be specific if you can. What holes do I use for what? There is a rusty spring lying around I believe was used for the stock carb. Shall this be used? if so where? Yeah you get the picture... If someone have made the same set up with a Edelbrock 500 Cfm carburetor (1404) and have photos, it might help me. And again I really appreciate all the support!

 

[Mosesatm]

The linkage attaches to the smaller hole just below and to the right of the large hole. I’m not sure you’ll be able to use the clip, though. Just remove it and set it aside for now. You’ll also need a return spring that attaches to the intake.
Neil uses this carb so maybe he has a good photo.

 

[Mosesatm]

Here's a photo of a 2V carb. The exact attachments are different for your setup but the concept is the same. Linkage on top and a spring on the bottom.

 

[franklinair]

I use the small hole (adjacent to the large hole) as Arlie described.
You have to modify the linkage as follows:
Remove the linkage rod and drill a small hole in the end that will go into the small hole.
(It should be a very small hole to allow a small cotter pin insertion.)
When the linkage rod is thru the hole, put a small washer and cotter pin to secure it.

Neil

 

[Jester]

Dear All,

Thanks a lot for all the support along the way. I decided to stick with the manual choke and yesterday we did the final connection of the choke wire and the linkage, filled up cooling fluid and new oil and filter. As anticipated their was a waterfall out of the thermo housing. After changing this back to the stock we turned the key and the engine fired up almost immediately and idled nicely. Now we just need to get all the crap out of the garage to get the car out for a test drive. As a big thank you to all that has chipped in with good advice and knowledge I send this photo of a happy boy and his car.