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  1. #1
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    Brake Servo heat shields

    I am re-posting this thread , as the original post was back in 2014, and it didn’t show up under new posts when I added it . It’s been a while since I put this post on the forum, because I have been steadily working my way down my ever increasing list of things to do on the cobra , and other issues have gotten in the way ,but I am finally nearing completion on my heat shields . I won’t go into too much detail because Tony would like me to write an article for the club magazine, but basically I started off making a few cardboard templates, then got hold of some left over 1.2 mm thick stainless steel sheet from a student project at work, and got one of the techs to cut it to shape and put all the holes in using a laser cutter. I don’t mind admitting, this was one of the most complicated, awkward, fiddly pain in the arse jobs I think I have done on my cobra, due to it's location ,but I think well worth the effort, as I will no longer have to worry about the brake servo /clutch cylinder and associated oil and pipes being cooked by the colossal heat given off from the exhaust manifold. I have managed to design it so that there is an air gap between the servo, shield and exhaust ,and still maintain air flow throughout the engine bay and out through the side vents .I have not quite finished making the brackets yet , so the shields in the photos are only loosely in place ,and not installed properly yet .












    Last edited by psh; 26-04-16 at 01:34 PM.
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing"

  2. #2
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    Is it going to work as a heat shield Paul, with all those holes in it? If stuck in traffic, won't the heat just go up through the holes?
    BIG TONE


    Mercedes SL owner, definitely NOT a kitcar owner like you lot!


  3. #3
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    There is probably an obvious and simple reason but why not wrap the manifolds instead to reduce the heat in the engine bay to start with? That's what I was planning to do.

  4. #4
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    I reckon the holes are there for some ventilation when on the move and that this arrangement will stop most of the radiated heat getting through.
    Cheers
    Steve

    My missus asked me to build her a Cobra! – How good is that!

    AK Gen2 chassis arrived 12/2/15
    http://stevesakcobrabuild.blogspot.com

  5. #5
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    I stuck reflective heat shield fabric direct to the servo,not had any problems in 2 years on the road.

    I would be more concerned about providing a heat sheild for the starter motor as some solenoids tend to get fried in a very short while.

    Rog

  6. #6
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    Quote Originally Posted by tonym View Post
    Is it going to work as a heat shield Paul, with all those holes in it? If stuck in traffic, won't the heat just go up through the holes?
    As an Environmental Physics technician, I can answer this Tone, you did ask 
    Yes, the holes are there to allow a small amount of heat to peculate slowly through the shield , but not enough to damage the components I am trying to protect . My design also allows the air flow to continue as intended .through the engine bay ,and out through the side vents ,which in turn also helps remove the hot air .The holes also stops the build up of heat on the underside ,which in turn would eventually heat the shield up to around the same temperature as the manifold itself. The shield would then radiate this heat across to the brake servo ,defeating the whole idea of the shield . The holes also help to dissipate the heat in the shield material itself ,because the temp of the shield material around the holes will be cooler than the solid section of the shield ,which is exactly why cobra side pipes shields also have holes.
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing"

  7. #7
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    Quote Originally Posted by JamesB View Post
    There is probably an obvious and simple reason but why not wrap the manifolds instead to reduce the heat in the engine bay to start with? That's what I was planning to do.
    I personally don’t like the look of wrapped manifolds and didn’t want to risk damaging the manifold due to excessive internal heat build-up caused by these wraps .I believe that the wraps are good to protect various under bonnet 'items' from heat, but not a good idea for the use of holding the heat in the manifold. For example, you can use the wrapping for the protection of fuel and oil lines, brake servo’s, clutch cylinders, wiring, covering a starter motor, like I have done already, etc. On the other hand, thermal coatings that are chemically and electrically applied to the manifold seem to be the way to go and do not seem to damage the manifold, but this I believe is quite expensive and time consuming.
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing"

  8. #8
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    Quote Originally Posted by JamesB View Post
    There is probably an obvious and simple reason but why not wrap the manifolds instead to reduce the heat in the engine bay to start with? That's what I was planning to do.
    I forgot to add, Cool air flow needs to be around the exhaust manifold, and insulating it with a wrap to hold exhaust heat in makes the manifold material surface temperatures reach near molten levels and so damaging it beyond repair . When you wrap the manifold you trap the heat in the manifold, but also suffocate the material that needs to breathe to dissipate heat for it's own survival, hence the holes in my heat shields.

    Engineers, Metallurgists, and other experts out there will state that there is no way that the manifold material can fail because it was designed to withstand the internal temperatures of exhaust gases. This is very TRUE! But, when the manifold is not allowed to cool (or breathe) so as to dissipate those extreme temperatures that the wrap is controlling, you have now developed a heat absorption that compares to thermal friction. This causes temperatures to continue to rise beyond the normal exhaust gas temperatures (EGT's) the manifold material was designed to withstand. This would result in you having to replace the manifold and cylinder head gaskets frequently,which would be quite costly and time consuming.
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing"

  9. #9
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    Thanks for the explanation

  10. #10
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    Quote Originally Posted by Peaches94 View Post
    I reckon the holes are there for some ventilation when on the move and that this arrangement will stop most of the radiated heat getting through.
    Correct
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing"

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