This part came with the carb rebuild kit but I am unsure where it goes.

For reference:
[chapters.corvair.org]

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++ Eastern North Carolina +++
++ 1964 Monza 900 Sedan ++
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That looks to be the vapor vent seal (Fig. 7). Ken

Ken Henry, Rochester, NY USA
1965 Corvair Corsa
140 hp, 4 speed

It depends on the year of your carbs.

LM carbs have a vent hole in the base of the carb.

The piece in your pic covers the hole - with a spring arm.

Found it. Thanks KenHenry and RobertC

++++++++++++++++++++
++ Eastern North Carolina +++
++ 1964 Monza 900 Sedan ++
++++++++++++++++++++

64 and later. Not just late model carburetors.

Frank DuVal

Fredericksburg, VA

Oh those 64s with a foot in each camp.

Jim Brandberg
Isanti, MN
CorvairRepair.com

I can't get the jet out. I used PB blaster and soaked it for a day. I used a propane torch to heat the jet until the carb was too hot to hold and still it's stuck. A friend suggested Kroil penetrating oil which I will try but it's probably a lost cause at this point. Looks like I'm on the road to using an extractor.

++++++++++++++++++++
++ Eastern North Carolina +++
++ 1964 Monza 900 Sedan ++
++++++++++++++++++++

I have a special screwdriver I use where the blade fits the slot well. I tap the top of the screwdriver with a hammer for shock.
I use a vicegrip on the handle for more turning force. With the carburetor in a large vice I can push down with one hand and turn with the other. Penetrating oil is good.
I heat the carburetor from outside and watch the oil boil a little. I don't heat the jet, I heat the carburetor with the idea being the aluminum heats up and expands away from the brass jet.
If I destroy the screwdriver slot in the jet I drill it out a step at a time until I can get the brass threads out of there or use a 1/4-28 tap.
I hardly ever use a screw extractor anymore, if it breaks off you're really screwed.

Jim Brandberg
Isanti, MN
CorvairRepair.com