I lost my spring. Please send photos!

Hi All: I've lost the spring that is on the stem of the counterweight shaft for my 1974 Duster's slant six exhaust manifold. I've attached a photo of the location where the spring was before I lost it. Does anyone know why this spring is there? What does it do? If you have the original one on your car, could you please post a photo? I could then get a replacement at the hardware store. As you can see, one end of the spring attaches to the end of the shaft, and the other end attaches to a fixed post on the exhaust manifold. Many thanks!

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I have several slant 6 exhaust manifolds. I'll look tomorrow and see if I have one. I'll send you one if I do.