Choke thermostat problem

French demon said
Hello Dan
If I understand correctly, when cold, the thermostat spring push onto the choke flap to close it and when hot this push slowly decreases.

Correct.

French demon said
In parallel, the vaccum pod pulls onto the flap to open it.

Yes, plus the choke flap is offset-mounted on the shaft, so when the engine starts, airflow past the flap pushes on the long/downhill side of the flap more than on the short/uphill side, thus pushing the flap open.

French demon said
In my case, the push doesn't decrease. At least, not a lot. The flap isn't fully open, but rather 1/4 open, and 3/4 closed.

The choke thermostat must be adjusted correctly, and you need the correct gasket thickness under the carburetor.

French demon said
I have the 1970 FSM (sadly not the 1971 one)

Close enough.

French demon said
and page 14-122 it talks only about "2 notches rich".

Yes. loosening the adjustment nut allows you to increase or decrease the spring pressure on the choke rod. There is a long central index mark, and shorter marks on both side of it. "2 notches rich" means the pointer on the movable part of the spring assembly should be aligned with the second short mark in the direction of more spring pressure.

French demon said
About the gasket, effectively it's thin. Around 3mm. But I have 2 or 3 other gaskets. May I pile up them to obtain the right height?

Yes, you can use 3 of those 3mm gaskets. Make sure they are all the correct kind, with two small bites out of the big central hole plus a 6.4mm hole off to the side which aligns with the 6.4mm hole in the intake manifold, next to the big main hole. Make sure all three gaskets are aligned correctly with the manifold and with each other.