I have a Ford and a Holley Vaporizer Carburetor both are essentially the same and I have always been told they are twins,but this is what I discovered during rebuild.
the Holley is using part # 6212 float needle & seat
but the Ford is using part # 6172 needle & seat for a Kingston L-4 here are pictures of where they are installed Holley first
then the Ford
The Holley is threaded cast iron but the ford seems to have some sort of brass insert that is threaded for the L-4 needle and seat. My question is is this normal or is this a repair made by a model T'er with more brains than money?
And you've owned them since new? I suspect the insert is a repair from years past. This is one place a Helicoil won't work.