The Carter YF 2100S is a replacement carburetor marketed for the Rochester B used on 1950-56 235 engines. What is needed between the flange and the intake manifold insulator depends on the insulator and it follows logic that you use whatever GM used from the factory. In the picture, the YF2100S flange will align (red line) with the recessed area on the insulator to be open to vacuum. No gasket is needed BUT both surfaces have to be dead flat with each other. What if the insulator has no recesses? Compare with the YF 966S (1950-52 235 engines). In a nutshell, you use 1A-31 (or equivalent gasket).
Carter went out of business back in the mid 80's. Gasket manufacturer's today try to make one flange gasket to fit a multitude of applications so the design of what is available adds to the confusion.
Last edited by buoymaker; 07/09/20224:43 AM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
