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Old 02-01-2009, 02:30 PM
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cooling engine compartment

HI guys,

I am new to the site and lot of informative information. I have a cobra kit car and am having problems cooling the engine compartment. I am not getting enough air flow through the compartment compared to the heat generated by the headers. There are side lovers in the body above the header but again not enough air. I thought about mounting a small squirrel cage blower the space above the header and directing the air toward the vents. I have not been able to find a small squirrel cage 4"-5" that can handle the heat from the exhaust. The space I have is above the headers. Does anyone know of any manufactures of squirrel cages made to handle the heat or have another approach to addressing this problem. I need to do this on both sides. I have noticed that most of the air flow from my radiator fan goes directly at the engine and then under.

Thank you for any assistance.

Mark

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Old 02-01-2009, 02:43 PM
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engine compartment cooling

I

This thread has been merged with the thread in the tech forum. Please, no duplication of threads.
Dan

Last edited by dinger; 02-02-2009 at 12:19 AM. Reason: Violation of guidelines. Please see: general board guidelines.
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Old 02-01-2009, 04:13 PM
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The easiest thing to do is to reduce the underhood heat by insulating the headers and exhaust. A thermal ceramic coating on the headers is also useful, but problematic if the headers are already old and rusty.

I doubt a small fan would move enough air to help.

You could look at ducting additional air into the engine compartment and/or adding vents at the rear of the hood to vent the air. I suspect that you problems would disappear of you ran without a hood, so the vents would help.
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Old 02-01-2009, 04:33 PM
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Thanks. The headers are ceramic coated. My understanding is that raping headers causes a problem with condensation and premature rusting from the inside.
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Old 02-01-2009, 06:24 PM
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You're right...wrapping isn't really a good trade off.

An ugly idea is to shim/adjust the hood up a 1/4".

Do you have a chin spoiler? Adding a chin spoiler will dramatically reduce pressure under the car and generate a very effective flow (and give you some downforce at high speeds.)
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Old 02-01-2009, 07:55 PM
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If the headers have a quality coating inside & out, wrapping them wont cause rust. It will be ugly tho'.
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Old 02-01-2009, 11:23 PM
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Mark
Here is a picture of my 53 XK120S with a SBC. Ceramic headers..very tight compartment..


I have an electric..shrouded puller for the radiator..and a flex fan pulley mounted to get flow through the compartment.
I live in Tucson..110+ summers..

I have cowled all the inlet areas to run all available ait through radiator. Behind and under I have ducted air up into compartment. I have experimented quite a bit using a infa red temp gauge to see where the heat travels an how to duct it out.
I used aluminum flashing (roof repair thin rolled) to duct air over my headers then down away before firewall. Once I like the result I replace by making more substaintial aluminum ducts.
I was getting vapor lock..so I attacked this way.
By carefully routing the available air..I have eliminated the vapor lock...and reduced underhood temps by about 50*
The best was with flashing OVER tops of header..but I Have not needed to do that yet.
The ducting also keeps engine heat off the firewall and my feet.

I even have fashioned a small duct atop the radiator. It spots spill over..but more importantly ducts hot air at rest out the grille.

I do have too much heat when the car sits as there is no flow..and am looking at small fans mounted in side walls to extract from near headers.
I am thinking perhaps computer cooling fans which operate in high temps..but water maybe an issue.

Hood louvers would be the best..as in an XKE. But I just don't want to cut that 56 year old aluminum hood.

The ducting does generate a lot of dust (here in the desert)..as there is a lot coming up from the duct behind the radiator feeding the flex fan.

You can see some of the cowling in front of radiator.

I clean the K&N often..

Last edited by Docc; 02-01-2009 at 11:34 PM.
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Old 02-02-2009, 08:26 AM
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Thanks for info.
I do not have a front lower air dam on the car. and you are right lifting the hood looks ugly.

Docc I noticed that you had a flex fan besides the electric fan. I had considered this option to see what of difference it would make. I think that I may try different methods of ducting air through the compartment and forcing it out over the headers.

The question I have is the only small fans I have found that seem to be in the size range of 4" x 4" are made of plastic and are for computers I also found some that are boat bilge pump exhaust fans and these too are made of plastic. My concern is with heat around the header area and compartment I am afraid that they may melt or get hot enough to distort. Any one know of any small steel squirrel cage motors again in the size of 4"x4"?

Mark
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Old 02-02-2009, 09:57 AM
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The best and cheapest I can think of is the heater blower motor from an older car when they still used metal instead of plastic. Cheap and easy access at a junk yard.
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Old 02-02-2009, 11:02 AM
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I think I would try to let heat out instead of trying to move more air IN. Is there a way of louvering any of the inner fenders to allow air to escape behind the front wheels? As far as fans go, there maybe something you could use from a heater, perhaps a low voltage fan from a fireplace insert, something to look into. Many have battery back-ups for power outages. Good luck, Dan
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Old 02-02-2009, 11:46 AM
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If you want a squirrel fan that can handle heat, then go to your local U-Pull-It type junk yard and get a couple injector cooling fans from a 280zx datsun/nissan (79 to 83). They are 4 or 5 inch squirrel fan and are mounted on top of the the valve cover (one per car).
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Old 02-02-2009, 12:07 PM
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don't try to "engineer your way around the problem"....

improve/modify/build the fan shroud so it does direct air off the inner fenders at a stop light for more air cfm on the pipes....
(with no shroud you are loosing 20%+ of the motor "and" compartment cooling!)

rig a switch to the brakes pedal so that the fan does come on period at a stop light...

what is the specific excess headers heat problem?
heat in the car?
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Old 02-02-2009, 05:14 PM
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Quote:
Originally Posted by Mark DeLuca
Thanks for info.
I do not have a front lower air dam on the car. and you are right lifting the hood looks ugly.

Docc I noticed that you had a flex fan besides the electric fan. I had considered this option to see what of difference it would make. I think that I may try different methods of ducting air through the compartment and forcing it out over the headers.

The question I have is the only small fans I have found that seem to be in the size range of 4" x 4" are made of plastic and are for computers I also found some that are boat bilge pump exhaust fans and these too are made of plastic. My concern is with heat around the header area and compartment I am afraid that they may melt or get hot enough to distort. Any one know of any small steel squirrel cage motors again in the size of 4"x4"?

Mark
Having the electric shrouded (complete radiator) for cooling..and the flex for more airflow through the very tight compartment has worked for me.
In 80* heat..I run 185*. In 105+..it will rise a little to maybe 195/200*..but cools well at speed. Temp is always stable.

The flex thows a lot of air through the compartment. Before I had the flex..
Temp at base of carb was 185*..after 135*
Temps at Master Cyls (Brake and Clutch) also are greatly cooler.
Before I added ducting I was getting hot air penetrating firewall..and cooking my feet.
With the foils after the header..aimed down that was greatly diminished..( I also added heat shield mat).
I measured heat in the areas..made a chart..then added these little foils and ducts.
My car has been back on road since 10/2006..here in the desert...without vapor lock..and much improved underhood temps.
All I can say is it worked for me..on my application.
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Old 02-02-2009, 05:17 PM
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The radiator electric fan is in a custom made shroud that covers the entire radiator. I will post a picture of the inner fender well where the headers reside so that you can see the space available. I will not be able to do this for a couple days. I think I will look into the nissan cooling fan.
Thanks everyone this site and all of you are a breath of fresh air with the willingness to help.

Mark
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Old 02-02-2009, 05:23 PM
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If you do use a flex fan and a electric..make sure they turn the same direction...keep the flow in phase. Out phase seems to diminish flow and induce vibration.
My radiator is a Griffin completly shrouded with 1850cfm fan.
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