[Mgs] MGB Stock Exhaust Manifold

[PaulHunt73]

According to the Parts Catalogue 709 is for 18Gx engines, 3911 for 18V engines, that change being in August 71.  It doesn't differentiate between North America and anywhere else, and although North America and other export markets got HIFs at the same time as the change in engines, the UK continued with HS carbs until 1974.  There were corresponding changes in the inlet manifolds for both markets, so I suspect the difference is in the thickness of the mounting tabs on each manifold - matching pairs being the same thickness, non-matching pairs needing a stepped washer where they share a bolt, something that is often discussed where modifications to exhaust and intake are concerned.

PaulH.
  ----- Original Message ----- 
  I found some HS4s in the dungeon and am replacing the weber and header on my 1968 GT, but still need the stock exhaust manifold.   I see the manifolds stamped with two numbers: 12H709 and 12H3911.  


  Is there a difference between the manifolds?  One for HS4s and one for the HIF carburetor?  My 72 MGB has HIFs and the 12H709 manifold.  I don’t think it matters.
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