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mon-thurs 9-5 cst
It's designed to have a larger pump area for the fuel pump diaphragm. This is why these carburetors are called high volume or, in some cases, double-stack or alky pump stacks.
The double-stack refers to the additional plate that separates the fuel pump and check valves making complete unit two plates or double versus the single plate that holds both. Do not mix single and double stack plates. The design, gaskets, and diaphragms are exclusive to each fuel pump stack and will not work if mixed.
They are also referred to as alky plates, but this is not accurate. The reason they are referred to as alky plates is for the extra volume required to pump methanol vs. gas. The most accurate description is to call them high-volume pump plates or stack. This is for engines running gas or methanol that require higher volumes of fuel to make the engine perform.
If you are converting a gas carburetor, you will want to use a high-volume plate. Using these plate are not the only modifications you need to make for your carburetor to run methanol.
91A-303 OE Tillotson Diaphragm Cover Plate fits all High Volume(Double Stack, Alky)Tillotson Carburetors. Check your carburetor and carburetor listing before ordering.