If I remember correctly there is a caged ball in that hole acting as a check valve for the inlet.

I used a heat gun, doesn't get that much heat but it seems to make the penatrating oil work better, just be patient, it will free up, now shaft and diaphragm comes with the rebuild kit.

I'll have pictures of my spare carb coming soon, I have it at the house. Dave

1941 Chevy
"First rebuild - complete!"
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1941 GMC resting peacefully
1946/1947 Chevy Street rod on s10 frame complete
1945 GMC panel truck in line for restoration
1941 Plymouth stock complete
1941 GMC COE in restoration process
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1941 Chevy Coe uncertain future resting now