Ok, here is a pic of a Holley 4180 somethin or other. I've got the same one on my 85 F250 2wd 7.5L with C6 automatic. What is this port near the choke that is circled in yellow? I know a hose connects to it, just wondering which one.

 

On my '87 it goes to the Vacuum Control Valve on the thermostat housing.
It is labeled "E" on my diagram and seems to control the EGR and A.I.R. bypass as well.

You should be able to find a diagram like this in your engine compartment.

 

i've been reading up some, and was wondering if it might be the vacuum choke pull off? in other words, it doesn't supply vacuum, the vacuum control valve (VCV on thermostat housing) opens after coolant heats up and takes the main vac pressure (red vacuum hose) from the manifold, and pulls the choke open as a secondary backup? the diagram routing also shows this may be true. i think i'll go out and see if that port pulls any vacuum through all rpm's and temperatures.

i'm in the process of eliminating and/or replacing all the dry and cracked vacuum hoses. this is the only port that i can't figure out. just doesn't seem right to be the EGR or A.I.R. supply being way up on the top of the carb like that.

 

I think your interpretation is correct.

I had to replace a bunch of my dried out plastic hoses and ended up buying paint markers from the art supply store to mark the ends of the black rubber hose

 

What conclusion did you come to?

I have this port connected to my vacuum tree on the firewall (One hose to the A/C and heater controlls, one to the intake for full manifold vacuum, and one going to the port I believe you are refering to on the carb)

The way I have it setup this port is essentially a vacuum leak for me. The manifold vacuum is pulling air out of this port.

Since your picture is no longer up I just want to make sure that this is the port you are refering to? (the port by the choke pull off.. my truck doesn't have a pull off though)http://image.mustangmonthly.com/f/mi...no-subject.jpg

 

The one facing forward is ported vacuum, I believe.
Simple enough to put a gauge on it and see how it behaves as you open the throttle plate.
I often use my MityVac for things like this.

Do you have a vacuum routing diagram on your radiator support Sw1tchfoot?
Is yours an aftermarket universal 4150/60?
I think all the 4180's have the vacuum pull off shown.

 

My truck came with a 2bbl carb so my diagram is incorrect. I'm not sure if my carb is from a Mustang or from a truck, but I know it's a 4180.

I have figured out every port and detail about this carb (basically..) except for this one:



It doesn't seem to pull any vacuum as far as I can tell. I know it's not for vacuum advance (the small skinny port under the front fuel bowl is for the advance..), my only guess is that it's a fresh air port just like the one right next to it that I know is a fresh air port (for the choke). I was just hoping that I could get someone to confirm, because nobody seems to know

 

If you put a gauge on it and it shows no vacuum at idle, high vacuum at small throttle openings and less as the throttle opens, then it's ported vacuum.

If you have nothing to hook it up to just put a cap on it.

 

I decided to cap it, it seems like a useless port..

It pulls no vacuum at idle, or above idle.

I'll have to look closer at a friends F150 sometime, it has a 4180 and everythings is untouched.

Thanks.

 

Could just be to cool the choke element and prolong it's life in that case.

 

That is the EGR vacuum port. If you put a vacuum gauge on it and blip the throttle it will read vacuum for a second then return to zero. There should be a 2 port vacuum temp sensor located somewhere on the cooling system, probably the upper radiator hose outlet, which prevents the EGR from working until engine temp reaches 150 degrees. Simply connect one hose from the carb EGR port to temp sensor, then another from sensor to EGR valve and your in business.

Your welcome in advance!

 

On mine it is ported vaccum for the distributor advance.

 

Thanks for the replys.

Mine must have a problem or something then

My vacuum advance is non functioning when connected to that port. It works just fine when connected to the vacuum advance port below the fuel bowl.

 

i'm thinking beetle has answered our question. and if i remember right, the broken hose that was coming off of this port was pointed backwards toward the EGR. since i did away with mine, i just capped it. oh, and yeah, that is the same port that was in my original pic.

 

You could get away with just by-passing the ported vacuum temp sensor by connecting a hose from the EGR to carb vacuum port. It would probably stumble on acceleration until the engine warms up.