Twin H intake block off plate

I am in the process of replacing the intake manifold on my 52 308, still considering installing an exhaust header.
Anyway, I understand one of the faults with the stock exhaust manifold is the heat is transferred to the intake manifold via the heat riser chamber. I seem to recall a post where the fellow installed a metal plate to seal off the passage of exhaust gases up into the intake manifold. Seems like a good idea, wondering how thick the plate should be, also is it necessary to use a gasket on one side to stop exhaust leaks?
Wonder how a copper plate would work, may be able to leave out the gasket ?


  • super-six
    super-six Expert Adviser
    I made one from stainless steel. One I had made earlier from sheet metal rusted-away.
  • 50C8DAN
    50C8DAN Senior Contributor
    I have headers on my '54 with Twin H.  I have not had any issues with having the intake without any block off plate.  However, in the new 2x2 intake we are designing, which will be Al not cast iron we plan to offer a block off plate for anyone still using the stock cast iron exhaust manifold.    It will not be necessary with headers as there will not be any connection between the intake and exhaust with the new design.
  • dave11
    dave11 Expert Adviser
    Tks guys