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headers: shielded or unshielded

Discussion in 'Technical Q&A' started by 1972 #04128, Jan 20, 2012.

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  1. 1972 #04128

    1972 #04128 Rookie

    Jan 20, 2012
    4
    #1 1972 #04128, Jan 20, 2012
    Last edited: Jan 20, 2012
    My factory original US model 246GTS headers shields are rusting away. The original shielded headers are no longer available. I was told that the unshielded headers (Euro version), were the proper replacement. They said that the shields were only needed for the smog equipment because of the high heat generated by the air induction for smog testing. As smog testing is not an issue, the smog pump was removed years ago. Is this correct? The inboard exhaust runs very close to the fuel cross over. Will an unshielded header create too much heat for the fuel line. If unshielded, should it be heat coated? Thanks for any help. SAM
     
  2. BigTex

    BigTex Seven Time F1 World Champ
    Owner Rossa Subscribed

    Dec 6, 2002
    79,406
    Houston, Texas
    Full Name:
    Bubba
    #2 BigTex, Jan 20, 2012
    Yes and no...the intent was to cook off unburned fuel (using the air injection) leaving the head.

    They are right, bare ones and (Jet Hot coated) will work well.

    I agree with you that fuel line routing should be carefully examined and protective means used to avoid problems.

    My outer skin on the 308s was aluminum???

    It does get loose as the asbestos inside packs down and disintegrates.
     
  3. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    9,742
    #3 Mitch Alsup, Jan 20, 2012
    To shield or not to shield, that is the question.........

    A header will last longer if it is allowed to transfer heat to the air. The <rest of the> stuff in the engine bay will not. So shields are used to protect these other parts from excessive heat (mainly radiative IR).

    Coating the insides of the header prevents copious amounts of heat from getting into the metal of the header. Coating the insides 'may' smooth over some rough welds.

    Coating the outside of the header prevents copious amounts of heat from leaving the metal of the header. <Some people think> Coating improves the looks.

    Thus, ideally, headers should be coated on the insides but not on the outsides, but no coater does only the insides without doing the outsides !?!

    Even with coated headers, the other parts in the engine bay should be shielded from the heat.
     
  4. 1972 #04128

    1972 #04128 Rookie

    Jan 20, 2012
    4
    #4 1972 #04128, Jan 22, 2012
    I have pretty much decided to take both of your suggestions. I am going to coat the headers, then I am going to have the original shields dublicated. They are constructed in segments and my fabricator says he can do the work in a few hours. I did not like the after market shields I saw, so this seeems the best to keep that original look.

    Yes, my 308 had aluminum shields, but the 246GTS has very thin steel ones.

    Thanks again SAM
     

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