scv carb (or not scv??) question w/non-loado dizzy

[kuhlou]

1966 Mustang, CA smog equipped, non-loado dizzy ID'd per prior thread. I assumed the Autolite 1100 carb mounted was an SCV model, since there was an SCV valve screwed into the carb. On advice in a prior thread, I removed the SCV valve to plug the hole, and behind the SCV, the big port was blocked! Factory blocked off, however, the small port that runs to the venturi below the throttle was there, so rtv'd that closed, and plugged the scv with a stopper/rtv combo. Removed the carb from the adapter, and another vacuum source was revealed! In the carb adapter, a groove was cut to the hole in the carb mount (manifold vac?), and this groove aligned with a small hole in the bottom of the carb mount flange.



Here's the carb mount gasket.



Bottom of carb mount, see small hole.



I don't recall seeing this addressed in any of the posts I've read? Does anyone have an idea what this port if for? Block it off? Leave it?

I was only going to modify, because I assumed I had a mismatched SCV carb with a non-loado (verified) dizzy. Going to use the carb just to get a DSII installed and running. Then, install the HW 5200.

Learn something new everyday I guess. Can anyone shed light on this one?



Thanks

Album link: http://s284.photobucket.com/albums/ll38 ... te%201100/

 

[ludwig]

I believe that it pulls the heated air past the bimetal spring for the choke pulloff. Keep it clean. If it is filled with soot, you have a burn through in the stock manifold where the air is heated.

 

[jamyers]

I believe that it pulls the heated air past the bimetal spring for the choke pulloff. Keep it clean. If it is filled with soot, you have a burn through in the stock manifold where the air is heated.

Yup, vacuum passage for pulling hot air through the choke.

 

[kuhlou]

okay, it did look like that port led to a runner toward the choke. Thanks for the help. Looks like I did a pretty good job messing up the pictures that were to appear in this post as well!

 

[kuhlou]

I sealed off the vacuum port on the log with rtv for the choke. Made a big difference in vacuum, went from 15 to 18, idles much more smoothly. Only drive car in the warm weather, so I'll get along with no choke. Hopefully, will get new dsII setup and hw 5200 install going soon. Is there an electric choke made for the autolite 1100 carb?

 

[66 Fastback]

That is interesting to know about the engine vacuum picking up. I wonder how many dravability problems are caused by too much vacuum leakage in the choke circuit.
Doug

 

[kuhlou]

In my 42 year old mustang, the heat tube from from the exhaust manifold had some sort of sealer on it, it was all dried and cracked and the heat tube pulled right out of the exhaust manifold when I unscrewed the tube from the choke. Aha! leak source. Also, the nut securing the tube to the choke was frozen, and I doubt if it could hold a vacuum even if the exhaust connection was tight. In my haste for a ride, I forgot to plug the hole in the exhaust manifold. I assume that hold did not go all the way into the manifold, but if it does I have an exhaust leak now. Will have to check that out.

 

[wallaka]

In my 42 year old mustang, the heat tube from from the exhaust manifold had some sort of sealer on it, it was all dried and cracked and the heat tube pulled right out of the exhaust manifold when I unscrewed the tube from the choke. Aha! leak source. Also, the nut securing the tube to the choke was frozen, and I doubt if it could hold a vacuum even if the exhaust connection was tight. In my haste for a ride, I forgot to plug the hole in the exhaust manifold. I assume that hold did not go all the way into the manifold, but if it does I have an exhaust leak now. Will have to check that out.

It is not supposed to be open to exhaust, but cracks can form there. I'm sure you would have known if you have run the engine before.