The 2100, whether you use the “S” on the end or not….is a 235 carb. Most/all of the stampings I have seen have the S, sometimes very faint. But I’m 99% certain a 2100 is the same thing with or without the S.
See the tech tips section in this forum for Carbkin’s complete listing of Chevrolet-application YF carbs. You will not see 2100 listed for a 216.
Edit: Upon further review, the listing of Chevy carbs in the tech tips doesn’t list the 2100 at all. Only the 2101, which is the auto choke cousin of the 235.
However….see the attached document for 2100(s) application.
