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Carburetor 38 Century

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Generally speaking (again, so defer to the Buick shop manual if it contradicts me)


The weight should never be down, in fact probably straight up when cold


The thermostat spring will not be in place when you weld it. Unhook it from the post.


Cold position should direct exhaust up under the carb. Look up under there. There are probably 2 ports up under the intake. With the plate in the cold position (and the weight straight up), the plate will direct the exhaust up into ONE of the ports, somehow there should be a path from the other port on down and out. Most likely the top plate will just stop with its top edge between the ports.


Hot position will most likely have the weight pointing straight at the engine, maybe ever so slightly up, (if the riser travel is less than 90 degrees it will be a little up). The plate will be at an angle that directs the exhaust coming from the engine down. This is the bottom-most picture in MCHinson's post. Flip the picture sideways.


The shop manual should tell you how tight the thermostat spring is. It is probably half or 3/4 of a turn. Wind it up however much the book says and hook it over the post.


If it gets tighter instead of looser with heat, the spring is on upside down. Take it off and flip it over.



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Yes, that is my photo from my 1938 project. That is the engine cold position. The weight should be almost vertically up towards the top in that position. Your photos look like the valve in that aftermarket valve body was not welded but was held in position by two cotter pins or other steel pins that have rusted away. Match it all up to the service manual diagram and you will probably see some small rust stains that will show you how it was previously aligned. I would simply tack weld it, or I guess you could drill out the old pins and insert new pins. Mine in the photo above is an original one. It was rusted shut and the valve was loose, I was able to see where it was supposed to be and simpy tack weld it where the original welds had broken.  

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To go with the photo above of the valve in my 1938 Century, here is a photo of the engine cold (heat on) position from my 1937 Century. I don't know if the bottom spring attachment is lined up like it should be but the manual indicates you bend the tab to get it adjusted as needed. It works fine like it is for me, so I have never changed anything about the spring attachment.


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I think this may be finally figured out with all your help here, thank you! I positioned the 2 cotter pins in the plate and I believe it sits where it should be, touching the bottom of the wall, weight up... The next thing was the heat test  (Used a small torch) and it wasn't long before it easily moved the weight back!..:) Mathew, thank you for the additional photo and Bloo for the detailed explanation...


Heat off Spring position.JPG

Heat off.JPG

Heat On.JPG

Edited by philipj (see edit history)
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