1. pishta

    pishta I know I'm right....

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    good question. I know NOx formations happen at high temps (so they dilute it with cooler EGR ) but I think those events are so short that the heat is immediately quashed by the inrush of: cold fuel, inlet air, and EGR so the average temp is well within the AL working zone. Also with the EGR and EFI, exhaust temps are probably very tightly controlled. Temps would be a little looser with a 1920 Holley but were still talking a 7.5:1 110HP slant.
     
  2. my68barracuda

    my68barracuda Well-Known Member

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    aluminum alloy is OK to use as a head or piston material, I cannot see why it cannot be used for exhaust manifolds.

    pistons whether 2 cycle or 4 cycle get cooling from the incoming fuel - air charge as well as from the lubricating oil,
    many performance engines and most diesels have an additional oil jet that squirts oil on the bottom side of the piston to cool it.
    and remember, it is only the top of the piston that gets exposed to the combustion temperature, the skirts and under crown areas
    absorb the heat from the piston top and let the heat out to the rings and cylinder walls, but they do not get the direct combustion heat.

    cylinder heads, air or water cooled have provisions to remove heat, the water cooled heads have internal passages.
    The air cooled heads will have fins to increase the surface air for the heat to dissipate to.

    So certainly an aluminum exhaust manifold could be made, but for the manifold to have any realistic durability factor it would need
    1) substantial increase in wall thickness
    2) provisions for cooling, either a water jacket or cooling fins.
     
  3. RustyRatRod

    RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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    Not as hot as the exiting exhaust gasses by a long shot.
     
  4. famous bob

    famous bob mopar misfit

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    I agree, way higher temps than posted above . I have plastic hood vents in my fiberglass hood, on each side of the 6 pack scoop, the one on the pass side is starting to melt ? Big engine in a tite space. Have my cooling problem whipped , and tune is close to spot on----------
    Didn`t do it with header wrap, but does now w/o it !! I hate the dam wrap !!
    Guess I really need a new set of thermally coated headers>$$$
     
  5. pishta

    pishta I know I'm right....

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    wrap will move your tune a bit due to more scavenging. TB coated is the way to go, especially on the inside even more so than the outside. Wrap has its place, but it's not on the headers anymore.
     
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