Topic: Why the 91A and 51A head gasket difference


4t6v8    -- 03-31-2010 @ 12:15 AM
  I note the 91A type head gasket has 'triangular' or larger water openings than the 51A type. I have a C59A engine, would fitting the 91A type be better to assist with cooling or water flow than the correct 51A type.
I am just curious on this issue, so would be interested in any comments, particularly that the 51A holes are a lot smaller, so why is that for the later model engine. Thanx Keith




40 Coupe    -- 03-31-2010 @ 6:36 AM
  do not use the 91A head gasket with your engine. these gaskets were reworked and ford brought out the 41A gasket which has a better style cooling passages. The smaller water passages are toward the front of the block forcing more water toward the rear and improving cooling in that area. the gaskets are market "front"


supereal    -- 03-31-2010 @ 6:59 AM
  The old 41T gasket was superceded by the 59A style. The old gaskets have three large trapezoidal openings at the center, and the new kind have a larger round hole in the center place, with a small round hole at the bottom. This is matched by drilling two of the holes in the head at the center. The top hole is enlarged to 3/4", and the third from the top to 5/8".


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