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Technical How to reduce under hood heat

Discussion in 'The Hokey Ass Message Board' started by rockable, May 6, 2019.

  1. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
    ALLIANCE MEMBER

    I just used that for an example.
     
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  2. G-son
    Joined: Dec 19, 2012
    Posts: 504

    G-son
    Member
    from Sweden

    Flexible materials should be used. No harm done if they hit the ground.
    As for the air flow under the car, I may have to dig out my race car aerodynamics books, but if I remember correctly reducing air flow in under the front of a "normal" car with uneven floor can REDUCE aerodynamic drag (and increase downforce/reduce lift, and increase air flow through the radiator/engine bay). All the uneven surfaces, axles, exhausts etc. under the car cause a lot of turbulence under the car and cause drag, when the amount of air coming in there is reduced that problem is also reduced.

    A flat floor with the appropriate profile between the ground and the floor can be much better for aerodynamics, but creating that while keeping engine, transmission, rear axle, brakes etc. cooled and letting air out from the engine bay is a much bigger project, and not really what you would do on a custom/hotrod. A simple plastic air dam may do much more difference relative to the amount of work needed to build it.
     
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  3. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
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    You and I are on the same thought train. I fabricated a plastic under tray that will block the air and turbulence under the front from going up in front of the engine. It terminates at the air dam and should work well to improve the flow out of the engine compartment.....hopefully. I will paint it black if it stays. 0511191153.jpg
     
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  4. Hutkikz
    Joined: Oct 15, 2011
    Posts: 77

    Hutkikz
    Member

    That makes more sense and addresses the biggest concern I had in your choice of position for your air dam. You lose the advantage of pushing air up into the rad but it should at least improve draw through the rad.
    I hope that you update this after you have a chance to test it.
     
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  5. Rex_A_Lott
    Joined: Feb 5, 2007
    Posts: 862

    Rex_A_Lott
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    Someone already mentioned it. Your flaps are too far back to accomplish what you want. You have the right idea, but where they are will force air up into the engine bay. The flaps need to be mounted underneath the radiator, to make the air stack up , and go through the radiator, and will help with the ram effect you are after. They need to hang down below the bumper to do much good. Later model cars had this type of setup from the factory, and were made out of some tough but flexible kind of rubberized plastic, for speedbumps, driveways etc.
    Nice car, good luck.
     
  6. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
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    Not with the tray, it won't. It also is not going to scrape the ground before my front sheet metal does. :) There already is a "scoop behind the grill that forces air through the radiator. The ram air setup is as good as I can get. The fan and shroud may be impeding the airflow, however. First drive yesterday seemed promising. Saturday, it's supposed to be hot. That's when I will really know, for sure. I'm still probably going to wrap the headers to cut down on the heat, as well.
     
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  7. gnichols
    Joined: Mar 6, 2008
    Posts: 10,400

    gnichols
    Member
    from Tampa, FL

    Anxiously awaiting your test results!
     
  8. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
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    Ok. It got up to 86 or 87 yesterday and today. I took a road trip on the interstate. The temps in the morning, when it was cool, stayed on 180 degrees on the button. Coming back in the afternoon, it got up to about 200 at 70 mph with the fan running. This was a slight improvement over prior to installing the under tray and air dam. I also removed the cowl lacing and put a few rubber bumpers in its place to create a very small (1/4-5/16") opening at the rear of the hood.

    I noticed that once I got out of 5th gear, into 4th and got on secondary roads, the temp went down to about 190. So, I took that as an indication I was a tad lean in cruise mode. I richened my Edelbrock 1406 up a step and retested this afternoon (#22 on the desktop chart). That brought the temp down to 190 at 70 mph sustained driving.

    I sat in a drive through line and the temperature came down to about 185-190 with the A.C. on.

    After reading an article on my Champion 3 row radiator and talking to the Cold Case rep, I believe 49 Ford is on point with my fan selection, so I'm going to try the one he suggested. I believe that will show me more improvement.

    Just to answer a question that has already been asked, the ignition timing is at 34 BTDC with the vacuum disconnected and the distributor on it right now has a 17 degree vacuum advance. (I also have a 10 degree.) The gas mileage is not what I'm used to on my 350 Chevy, for sure but it runs strong. So I will keep testing and tuning.

    I am holding off the header wrap, for now.

    Thanks for all the suggestions.
     
    Last edited: May 19, 2019
  9. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
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    Well, shit. I discovered today that the vacuum advance on my new distributor is not working. So, it looks like I'm starting all over. Jesus, sorting out a new car can drive you crazy.
     
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  10. lippy
    Joined: Sep 27, 2006
    Posts: 3,919

    lippy
    Member
    from Ks

    That sure could be it. Plus I don't think you even need or want a fan at 70 mph. Been kinda following along. LOL. Lippy
     
  11. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
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    I Don't want a fan at 70. That's been the goal from the start. Stay tuned.
     
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  12. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 335

    Elcohaulic
    Member

    When I swapped radiators, I broke the shroud in the process. I never replaced it. My under hood temps went down considerably without the shroud. I had to raise the thermostat from 160 to 180.. This made me a believer in Champion aluminum radiators!

    Try removing the shroud (if possible) and see what happens..
     
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  13. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
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    I've thought about doing just that. Thanks for the feedback.
     
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  14. I had a steel fan and no shroud on my '59 Ford. It ran hot very quickly in traffic and would boil over when I shut it off. Radiator is a 3-row Champion aluminum, stat is a 180* Mr. Gasket. Added a shroud, very little difference considering the expense and fabrication, I was probably into it for $160 to modify a bought shroud and materials to mount it.

    Ditched the steel 7-blade fan, went with a $40 Summit flex fan with good reviews. That helped my running around 180* temp to 175*, I was able to sit it traffic a lot longer. Fan is set into the shroud correctly.

    I added a Spal 16" pusher electric fan just in case I got stuck in some real heavy traffic (going to cruise nights, etc) and that has a t-stat. It comes on at 200*, off at 175* and I'm pleased with it. Before I shut the engine off, I make sure the fan is off and has done its job.
     
  15. nunattax
    Joined: Jan 10, 2011
    Posts: 1,680

    nunattax
    Member

    got to agree with you about the spal 16" fan .it dissipates huge amounts of heat when its running.
     
  16. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
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    Well, I received the Spal fan with the fatter blades. Unfortunately, I will have to get rid of the shroud, if I use it. After discovering a distributor vacuum advance failure, I am hoping I don't have to change. 90 degree days this weekend will help me decide.
     
  17. patterg2003
    Joined: Sep 21, 2014
    Posts: 500

    patterg2003

    You built the lower air dam to draw air out of the engine bay. There is no picture of the top of the rad. So the question is there an upper grill air deflector to stop the air from going up over the rad into the engine bay? The upper air deflector holds the high pressure in front of the rad for better cooling. One thought among many.
    This is an example of one for the Ford installed. Would not take much to make one.
    http://sullivansgarage-com.3dcartst...-Stainless-Air-Deflector--by-Drake_p_773.html
     
  18. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
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    Yes, the area in front of the radiator is well sealed. Thanks.
     
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  19. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
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    Ok. It finally got hot here and I tested every idea I had to no avail. I tried with and without air dam, inner fenders, etc. In desperation, I called Champion yesterday. George said that since it will actually cool down when sitting still and get hot while running at speed, he was convinced that it was an airflow problem. He suggested removing my shroud.

    Today, I did just that and Shazam!, the temperatures went down. My design was apparently restricting airflow at speed. At 91 degrees today, it stayed right on 180 for 2 30 minute drives. It also stayed cool while idling with the A.C. on.

    So, a fully enclosed shroud is not always a good idea, especially with an electric fan. A shroud that incorporates flaps is probably the best design but my radiator is only 18 x 18.5, so there is minimal room for flaps. Turned out that the 16" Spal fan I had moves enough air to keep it cool sitting still without the shroud.

    Thanks for all the ideas and tips, everybody.
     
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  20. G-son
    Joined: Dec 19, 2012
    Posts: 504

    G-son
    Member
    from Sweden

    Pics of the shroud?
     
  21. On my OT car with dual Spal fans, the shroud has a bunch of rubber flaps that is sucked shut when the fans are running, but opens (i guess) when i'm driving down the highway and the fans are off. I've been wondering about these flaps, and I guess this is the reason that they are there. Anybody knows for sure?

    fans.jpg
     
  22. G-son
    Joined: Dec 19, 2012
    Posts: 504

    G-son
    Member
    from Sweden

    Yes, that is the purpose.
     
  23. stubbsrodandcustom
    Joined: Dec 28, 2010
    Posts: 1,030

    stubbsrodandcustom
    Member
    from Spring tx

    Man glad you found the combination that works for you...

    I have a derale dual fan setup with their shroud with 2 flaps in it to "help" airflow... it works ok but before ac etc my under hood temps were not bad, now with this fan setup it is borderline... nothing near what you had, But still something to be cautious about. On power tour in 16, I had a fuse pop on my fan controller... 40 amp fuse... Pulling off the Kansas City Turnpike temps shot up to 240 on my 318 and I mean fast... Granted it was 100 degrees out but It really made me question the choice of fans on there. The modern cars fan shrouds are really not anything near what this aftermarket stuff is for our vehicles.. I have a little of the same issue you do on clearance for a mech fan... But I am going to go backward and make one fit again I think...

    I really like that splash shield you made there to help pull heat out though... I have considered it to help drop my under hood temps also... Just to keep the firewall a little cooler etc.

    Cool car and glad to see another guy running a SBM...…
     
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  24. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
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    Not deep enough and no flaps. 0531190931a.jpg 0531190931.jpg
     
  25. wheeltramp brian
    Joined: Jun 11, 2010
    Posts: 681

    wheeltramp brian
    Member

    I built one similar on a 49 Plymouth with a baby hemi.got very hot on the highway but fine in traffic.took it off and it fixed it.been that way for 5 years and no prob.
     
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  26. I had problem the further I drove the power level would drop and when shutting down for short periods car was hard to start . This was the fuel in carbs. boiling from heat . Tried 110 race fuel , power did not drop and would start up after short periods of engine shut downs . I now mix race fuel and hi-test gas and have good results , also car runs cooler .
     
  27. G-son
    Joined: Dec 19, 2012
    Posts: 504

    G-son
    Member
    from Sweden

    Agreed. You probably wouldn't need any flaps if it was deep enough, so the air flow from the corners could go towards the fan opening unrestricted.
     
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  28. rockable
    Joined: Dec 21, 2009
    Posts: 2,503

    rockable
    ALLIANCE MEMBER

    Amazing how hindsight is usually 20/20.
     
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