Auto Choke

[Jim Shepard]

I recently obtained a Stromberg WW 2bb (thanks Reg...) that I'm trying to put on my truck. The main issue is the linkage, but that's another story. This carb has an auto choke that is activated by some sort of heat riser on the exhaust manifold. Can someone post a photo of how this is attached/connected to the exhaust manifold?

[Joe Flanagan]

If it is a Sisson automatic choke, there should be two holes in the exhaust manifold where the bolts go. The holes should be close to the carburetor. There is also a gasket that goes between the choke body and the manifold itself. Don't have access to pics at the moment but will be able to post some this afternoon.

[Young Ed]

Jim does it look like this? If so I have one too and also don't know where the other end goes.

[oldmopar]

As Joe said two holes with bolts in the exhaust manifold also need a gasket to insulate choke from the manifold heat, then a wire goes to the starter motor. No photo I had one on my a few cars but remove them and set up hand chokes . The should be a photo in the service manual jus do not have my manual with me right now.

[Tom Skinner]

Here is a picture of a sisson automatic choke

[Tom Skinner]

Two Studs shown on left on top of exhaust manifold

[Jim Shepard]

Jim does it look like this? If so I have one too and also don't know where the other end goes.

I have the carb in Young Ed's photo. It looks like there is a metal tubing that exits the choke and goes somewhere. I don't think this is the same choke setup Tom posted, but I could be wrong...

[Joe Flanagan]

No, it's not the same. Different kind of choke.

[Young Ed]

I have the carb in Young Ed's photo. It looks like there is a metal tubing that exits the choke and goes somewhere. I don't think this is the same choke setup Tom posted, but I could be wrong...

My actual carb has this same setup too but the tube has been cutoff an inch or so from the carb. I suspect that it goes to a vacuum source somewhere I can't imagine what else it would go to. I've got a friend with a 55 plymouth convert. His car is a v8 but I'm going to call and see if his car has the same type of choke.

[oldmopar]

Why bother with the choke just remove it and go with a manual as it is a truck it had a hand choke originally. You can get a cable kit at NAPA

[Young Ed]

Jim here's what I found out. His 55 259 V8 has the same type of choke. The exhaust manifold has a tube that comes off and the pipe from the carb slips inside it. So it works like the sisson choke expanding with manifold heat its just a different style. You could have a tap welded to the exhaust pipe and put some sorta pipe on it. You'd have to leave the exhaust pipe alone so you didn't create an exhaust leak. You could possibly also hook it up where the heat riser goes.

[woodie49]

I believe that this tube is meant to attach to an impression in the exhaust manifold. I have attached a picture of the choke on my Packard which goes to the manifold to transmit heat to the choke unit. The choke looks similar to yours.

[Dodgeb4ya]

The 2BBL Stromberg carb setup uses heat drawn through a tube that goes right through the middle of the exhaust manifold. The bottom end of this tube extends into a metal steel chamber bolted to the bottom of the manifold which also collects heat. This open tube connects to the choke housing at the top end. When the engine is started engine vacuum draws a small amount of hot air through this stove pipe tubing. The exhaust gases heat up this 1/4" stove pipe tube. The clean hot air is drawn into the choke thermostat housing and Bi-Metallic spring. The spring unwinds as it gets hot and in turn lets the choke plate open. This 1/4" tube permanently fixed into the exhaust manifold will not let exhaust gases into it as the bottom open end of it is on the bottom outside of the exhaust manifold in that 1"X2" steel chamber bolted on the underside of the exhaust manifold. If exhaust gases were to be sucked into the Bi-Metallic spring the spring and choke housing would be full of black sooty exhaust and soon fail.

The round choke housing can be rotated CW or CCW to adjust how soon or late the choke plate opens.

The later 1957-9 Ply/Dodge cars with the 1BBL carters use this same choke system.

Bob

[Jim Shepard]

Ok, next question. I'll be using the cast iron headers from Langdon's, which have no provision for this choke. And I don't want to drill holes in the header and, otherwise, try and duplicate the factory design. Do you think the choke would work if I wrapped the 1/4" tubing around some part of the header or exhaust pipe? It seems that as long as there is a vacuum and the pipe is getting sufficiently hot that there would be hot air sucked up the tubing and operate the choke. True?

[Young Ed]

I cant say it'll work for sure but it sounds like a good plan!

[woodie49]

Ok, next question. I'll be using the cast iron headers from Langdon's, which have no provision for this choke. And I don't want to drill holes in the header and, otherwise, try and duplicate the factory design. Do you think the choke would work if I wrapped the 1/4" tubing around some part of the header or exhaust pipe? It seems that as long as there is a vacuum and the pipe is getting sufficiently hot that there would be hot air sucked up the tubing and operate the choke. True?

DodgeB4ya gave a great explanation of how this choke works. I am not sure how much heat is really required to completely relax the spring. It seems like tubing wrapped around the header would generate a lot less internal heat than one actually running through the manifold, so you might have a problem with the amount of time it takes to get the choke full open. Worth a try though.