58 Bonneville intake refurbish/mystery piece

[bjestes]

Does anyone know the purpose of the small tube from the center of intake on a 4bbl.  I believe it came off the carb, but the tube was twisted/gone.  It routes through the inside of the intake through another tube with a twisted flat metal piece inside.  A thermocouple of sorts?  And finally, I'll assume these parts are unobtainable, so what to do with the hole(s)?

[Bleach]

It's for the heated choke on the carb.

[carbking]

There was originally a steel tube pressed into the exhaust port of the intake manifold, more or less horizontally, which connected to a small chamber on the passenger side. A steel tube then connected this chamber to the choke housing on the carburetor.

 

There is a small internal vacuum passage inside the carburetor has causes the choke housing to have a slight vacuum. This vacuum then causes heated air to be drawn through the tube to operate the choke.

 

To slow the heated air, there was originally a twisted piece of metal, similar to an ancient piece of barb wire without the barb. You can see a piece of the original twisted metal in your picture.

 

The manifold may be heated, and the old steel tube driven out, and replaced with a new steel tube. When we were restoring tripower manifolds, we used stainless, but no longer have any inventory of the stainless. Plain steel normally is good for maybe 30 years.  The twisted tube may be fabricated from a piece of flat steel.

 

Don't know if the parts are available reproduction, as they are so easy to fabricate, but you might try Kelsey Pontiac Parts in Iowa Falls, Iowa.

 

Jon.

Edited November 13, 2018 by carbking (see edit history)

[bjestes]

Thanks Jon,

I was actually able to drill out the top piece of tubing, but am still working on the internal one.  I assume that the steel plug comes out to assist with the install of said tube?

 

Sooo, since I see you do carb. work, how about the original Rochester 4 bbl. for rebuild?  I know the tripower is sexier, but it came with the 4 and I'd like to save it.

Thanks,

Brian

[carbking]

Brian - no longer restore carbs due to the demand for the rebuilding kits we make, but give me a call 573-392-7378 (9-4 Mon-Tues central time) and will offer, if you wish, some pointers on the tube and the carb. That Rochester, or the original Carter 4-barrel, Pontiac used both, are great carbs.

 

Jon.

[GARY F]

Did you try Ames for that part?

[bjestes]

Nothing in the usual Pontiac suppliers catalogs.  Jon, I'll give you a call sometime about the rebuild.  The Rochester is original to the car, as they installed 500 in the end of 58. (According to Pontiac Service Bulletin).  Are these subject to warpage/distortion as some of the latter Rochesters?