1950 Willys Truck re-rebuild by 50wllystrk

3 minute(s) of a 620 minute read

Thanks for catching up, as you can see, we've gotten off the beaten path a little bit. Kinda left the jeep stuff behind for a bit and focused on how the jeep stuff runs.

You are quite correct, when properly tuned and adjusted, the automaticchoke does make life easier.

I only have two pictures so far. I took more but the camera didn't focus as well as I'd like.

The two pictures that I do have are of the part that is the heart of the automatic choke.

I hear it called a "choke thermostat" and "choke spring". Either way, it is made up of a flat wound coil. The wound coil is made by using two different metalic substances. The two metalic substances is called " bi-metallic", referrring to the two metallic parts.

The "bi-metalic" materials react at a different rate when exposed to heat and cold. With the two materials reacting different, there is a expansion/ contraction action that occurs.

The pictures will demonstrate better than words.

Here is the choke thermostat at room temperature. As far as the engine is concerened, this is at a cold temperature. The engine considers 180 to 200 degrees as room temperature.

Notice the loop at the end of the wound coil. This loop is where a piece of linkage will fit into when intalled on the engine. From this loop, the linkage will go upwards to connect to the choke mechanism on the carb.

This next picture is what happened when I warmed up the wound coil with a lighter. As soon as I applied the heat, the loop started to raise upward.

Ok, that's the idea. When the engine was cool, the wound spring contracted, when it contracted, it pulled a piece of linkage downward. The linkage then pulled downward on the choke mechanism, which closed the choke plate, shutting off the air going through the carb.

The choke thermostat is located on the intake manifold where there is a hot air passage that heats the wound coil spring. Once the wound coil spring becomes warmed, it expands. When the coil spring expands, it raises the linkage, which pushes upwards on the choke mechanism that will open the choke plate, allowing the air to flow through the carb again.

This one item replaces a manual choke cable.

My next pictures will show this process in action.

I've done enough writing tonight, but before the next write up, there is homework.

Just try to think back where you've seen carburetors with a round, black, plastic looking cup in the side of a carb. The diameter is around 2''. Any idea what is hiding behind the black cup?