Author Topic: Radiant heat protection  (Read 1031 times)

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Online Mad Max

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Radiant heat protection
« on: August 13, 2020, 08:36:38 am »
Hey peeps -

I am researching options for shielding some driveline components from radiant exhaust heat.  My build has some tight clearances where the 3" exhaust is about 1.25" away from a u-joint, and I do not want to 'cook' the grease inside the u-joint.  I'm either going to weld on a simple heat shield between the exhaust and u-joint or I'll clamp on a heat wrap barrier shield from DEI.  Whether or not radiant heat would actually overheat the grease in the u-joint is not the question - my question is which type of heat barrier would be more effective? 

A heat shield between the two components (1/2" away from the exhaust pipe) would certainly help and would probably be enough, and I'm certain the DEI wrap would also work but it might not last as long, plus it could get snagged and ripped off, so, I'm looking for any recommendations between the two.

Here is the area -



I only have 1.25" of clearance between them, and it'd probably be fine with no heat shield, but I'm going to install something and I'm leaning towards tin heat shield, but welcome feedback.

Tin heat shield (example pic from the web) -



DEI exhaust pipe heat barrier/blanket -

« Last Edit: August 13, 2020, 10:26:43 am by Mad Max »
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    Offline dodge82273

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    Re: Radiant heat protection
    « Reply #1 on: August 13, 2020, 09:41:12 am »
    both ?    the tin at a stand still will be hot due to no air movement , a wrap in should help with that , but grease turns to oil at a pretty low temp . I like the wrap with 1 side open too ....   two separated layers of tin with a wrap ? some factory ones have a aluminum sandwich with wrap inside .... 
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    Offline Elwenil

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    Re: Radiant heat protection
    « Reply #2 on: August 13, 2020, 10:48:02 am »
    I'd use an aluminum heat shield, preferably not mounted to the exhaust.
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    Re: Radiant heat protection
    « Reply #3 on: August 13, 2020, 12:04:33 pm »
    ...is header wrap typically used for reducing radiant heat...or more for 'performance' by keeping heat inside a header or exhaust pipe, etc?  IOW, would using header wrap  in this area actually do much good compared to a tin shield or blanket?  I'm not sure header wrap would really be of any good...
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    Re: Radiant heat protection
    « Reply #4 on: August 13, 2020, 12:16:51 pm »
    ...is header wrap typically used for reducing radiant heat...or more for 'performance' by keeping heat inside a header or exhaust pipe, etc?  IOW, would using header wrap  in this area actually do much good compared to a tin shield or blanket?  I'm not sure header wrap would really be of any good...

    I would not hold much value in it helping performance; it would be marginal at best. It is an insulator, but it can trap moisture against the pipes too. Personally, I would use the heat shield only. Look at how every car manufacturer does it. There are entire divisions of engineers that came up with that model (instead of wrapping the pipe).
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    Re: Radiant heat protection
    « Reply #5 on: August 13, 2020, 12:29:14 pm »
    yah that's along my thoughts as well...and I don't need the wrap coming apart/fraying, getting caught in the driveline, and then yanking the exhaust out of place and against the fuel tanks....   {no}
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    Re: Radiant heat protection
    « Reply #6 on: August 13, 2020, 02:47:10 pm »
    yah that's along my thoughts as well...and I don't need the wrap coming apart/fraying, getting caught in the driveline, and then yanking the exhaust out of place and against the fuel tanks....   {no}

    Or simply accelerating corrosion/rust
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    Re: Radiant heat protection
    « Reply #7 on: August 13, 2020, 05:02:04 pm »
    I am not a fan of any insulation or wraps put in contact with the exhaust system. I have seen several cars with a dual layer shield, Which is probably the direction I would go (one shield is good, two is better  ;)  ). That said, I have also seen several instances of an insulation used on frames and other components where they are near exhaust systems. Remember the hood insulation many of our trucks left the factory with? The next thing I would consider, is a spaced shield with a thermal layer attached.
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    Re: Radiant heat protection
    « Reply #8 on: August 13, 2020, 05:46:26 pm »

    The next thing I would consider, is a spaced shield with a thermal layer attached.


    ...my same exact thought too!  I have a ping to DEI for their recommendations...
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    Offline RXT

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    Re: Radiant heat protection
    « Reply #9 on: August 13, 2020, 06:50:53 pm »
    Aluminum is a fantastic radiant barrier. It's the best material to reflect infrared radiation. To be really effective, it has to be spaced from the source of heat and the component it protects. Even a sheet of aluminum foil can reflect up to 90% of the heat. Of course you would want to use something more substantial than foil.

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    Re: Radiant heat protection
    « Reply #10 on: August 14, 2020, 05:38:12 am »
    Header wrap does indeed contain heat.  If you paint it, you don't have as bad of corrosion issues, or fraying.  Now if you drag it on something, that will fray and tear it, but the stuff does work very well for what it is.  Put it on quality stainless and it wouldn't be such an issue, but even then, cheap steel headers have lasted me 10 years or so with DEI or Thermotec wrap, which is about all you can really expect from a set of cheap headers dunked in mud and daily driven all the time.  If I were really interested in moving the heat, I would wrap it and add a 1/8" thick aluminum shield.  The shield will work great, but it's most effective when moving so the air gap between the shield and the heat source can exchange the air and cool it.  Crawling on a trail, the wrap will be more effective in keeping the heat moving past the driveshaft.  Just my .02
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    Re: Radiant heat protection
    « Reply #11 on: August 23, 2020, 07:04:40 pm »
    Have the adjacent exhaust section ceramic coated inside and out?  Header wrap holds heat in so steel will burn out.  Ceramic on INSIDE keeps metal from getting hot to begin with.  Now you cant just do the 2" next to u-joint or conduction still get into the pipe metal, but if you do a decent length combined with a separate heat shield attached to frame and I think you'd be GTG. 
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    Re: Radiant heat protection
    « Reply #12 on: August 23, 2020, 08:45:35 pm »
    both ?    the tin at a stand still will be hot due to no air movement , a wrap in should help with that , but grease turns to oil at a pretty low temp . I like the wrap with 1 side open too ....   two separated layers of tin with a wrap ? some factory ones have a aluminum sandwich with wrap inside ....
    I've always used High Temp Disc Brake grease for my u joints.
    Maybe that's why they've lasted for over 16 years and still counting... now where is that wood? Knock. Knock!

    I'd vote shield. Two layers with a small space between to make cooling fins.
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    Re: Radiant heat protection
    « Reply #13 on: August 24, 2020, 07:58:26 am »
    all good inputs fellas - much appreciated {cool}.  Please feel free to keep the suggestions and recommendations coming.
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    Offline R!bcracker

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    Re: Radiant heat protection
    « Reply #14 on: August 24, 2020, 08:06:53 am »
    The heat shield would be better to save the u-joint, but is there room?  1/2 inch does not seem like a lot of space for the dynamic outline of the driveshaft or exhaust. 
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    Re: Radiant heat protection
    « Reply #15 on: August 24, 2020, 08:36:13 am »
    fortunately the driveline in this area is fixed - the shaft in the picture is fixed at both ends (t-case to carrier bearing) so it won't 'articulate' - that all happens a few feet back.  There's the normal driveline vibrations associated with a rubber-mounted engine/trans/t-case but other than that it's all relatively 'fixed'. 

    I'm intending to split the difference between the yoke and heat shield, and after talking at length with DEI I think I have a pretty solid plan: heat shield with their insulation on the exhaust side to dissipate/disperse the heat away from the yoke, and I'll probably go ahead and wrap it too for good measure.

    What's nice is, going slow there won't be much heat, so yayee...and going fast there will be more heat but also a whole lot of airflow...so yayee :) .
    « Last Edit: August 24, 2020, 08:48:56 am by Mad Max »
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
    1952 Willys M-38 "Poncho"

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