Okay. Assuming the correct gasket, the spacer seals the path in the proper gasket. There is not "canal" from the spacer to the throat that allows passage of vacuum to the carb. Am I missing something?
Actually, yes.
Please note in my previous post the different Carters that were designed SPECIFICALLY for early 1950's Chevrolet. The are dozens of later YF's designed for Chevrolet, and HUNDREDS of additional YF's for other applications.
The safe way is to use the carb specified for the specific application AND the specified gasket. If this is not done, then you need to know WHY the passage is in the carb. Some carbs were designed to provide a manifold vacuum port, others a ported manifold port for distributor use. Others were designed to have a passage to provide vacuum to a sandwich governor. Sometimes a passage would be used for dual purpose if the casting were used on different applications. And then you always have to contend with Dr. Goodpliers (the evil twin of Mr. Goodwrench) who thinks castings may be interchanged among carburetors.
When using other than factory engineered parts for the application, one becomes ones own engineer. One can always disassemble the carb, and determine the origin (or the object) of the passage.
So while your question about notching the spacer is a simple question, there is no single answer because of the different applications.
As stated in my first post, if you use the specified gasket for the carb, then the carb will get all of the vacuum the carb needs without providing any other help. Now whether you get the desired distributor vacuum, governor vacuum, etc. depends on the application.
Jon.
