Vacuum hose routing

[alini]

Im waiting for the carb rebuild kit to get here, I just went over all my connections to make sure I have it right in my head.  I had made a 'wire diagram' of where I disconnected things but I missed something somewhere.  I know the front carb port goes to the distributor, I know the back of the carb has the tranmission vacuum line, which threads in and the T fitting for PCV and Brake booster.  The manifold port at the back of the intake is for accessories (goes to my vacuum canister on the firewall and AC stuff)  I can not account for this one fitting.

 

At the top of the carb is a vacuum port that points toward the passenger seat.  I can not account for it.  In my 'Before' pictures, I find it had a hose that was broken, which was hooked up to a steel tube that traces down to the exhaust manifold.  This is NOT the choke tube, I have that accounted for.  This tube terminates that the fourth port of the exhaust manifold in the pics.  I found there is a threaded port in the exhaust manifold but doesnt seem to open to anything.  My other problem, I cant find the tube.  Im out of parts, I only have a few things left around the garage and I can account for each of them.

 

[alini]

I just pulled the vacuum canister out of the storage box and it has TWO ports, is that for the second connection?  Still doesnt explain the threaded hole in the manifold

[RivNut]

Vacuum modulator on the transmission comes out of the bottom on the back of the passenger's side.   A steel line threads into it and goes down the back of the engine.  Look for a tube that has a tang on it that will bolt to the back of the head or to the bell housing - I can't remember which for sure.  

 

The fitting at the top of the air horn goes to the bottom of the choke tube that runs through the exhaust manifold.  The choke tube goes from the top of the manifold to the choke.  As far as I know, there are no threaded fittings in the exhaust manifold.  

Edited May 27, 2015 by RivNut (see edit history)

[alini]

I can account for that and I have the tube for it.  Its the one at the top in the pic I dont know where it goes.  I also cant find that tube that I have in my pictures

[RivNut]

I have one set of manifolds with that "port" and two sets that don't have it.  There's a boss on the other two but no hole.  The one set that I do have that has that threaded "port" looks to me as if there's a bolt broken off in it.  I'm thinking now that perhaps it's a mounting boss for something.  There wouldn't be any vacuum at that point.  Some vacuum through the choke housing is pulling fresh air through the tube that goes through the exhaust manifold but there's no way that vacuum could be pulled from that "port."  If it were open, it would only allow exhaust gasses to escape. There's no vacuum at the top of the carb, it's just a fresh air inlet for the hot air choke.

 

Gord Wolfgang has a very pristine '65; perhaps he can tell you something more by looking at his car.

 

Ed

Edited May 27, 2015 by RivNut (see edit history)

[msdminc]

Chris,

 

The port on the back passenger side top is attached to a rubber hose and subsequently attached to a steel pipe that goes to the front/under side of the Choke Heat Tube connection of the exhaust manifold.  There is a clip on the valve cover that holds the pipe.

 

There are two connections for the choke heat tube to work correctly - one from the choke to the back/top of the exhaust manifold (usually has a braided white cloth covering) and one from the carburetor to front/bottom of the exhaust manifold.  The choke heat tube is actually a through passage in the exhaust manifold and these pipes are connected to the ends of that passage.

 

I believe this set up is the same for Rochester and Carter carburetors, I have a Rochester.  

 

I am not sure what the hole that you point out is, mine does not seem to have that hole.

 

Hope this helps and Rock On

 

gord

[alini]

Thanks Gord that seems a bit counter productive though. The vacuum port while not vacuum all the time would still have some vacuum at it under throttle so it would suck air away from the choke

Doesn't matter I'm switching to electric anyway so I will cap it

[RivNut]

Chris,

 

Did you take a closer look at the port in question?  Does it look like a mounting boss for some kind of bracket?  

 

The carb is drawing fresh air through the air cleaner.  Some of the air is channeled through the tube on the air horn.  The slight vacuum coming from the choke housing pulls that air through the choke tube circuit.  If you're going to run an electric choke, you can cap the tube off or just leave it.

[alini]

I tried feeding wire through it to see if it was connected to the heat tube. It's just a bolt hole but I don't know what would be bolted to the manifold in that location. I was thrown off because in my pics the tube hooked to the carb port was pushed into that hole so it appears as if it was intended for something

[Guest Dale in Vancouver]

Hi Chris. I puzzled over the same hole for a while. Came to the conclusion it's for a bolt to hold a clip for the steel line that goes to the bottom manifold "port". Cheers,  Dale.