Technical How to reduce under hood heat

This would be a last resort. An extreme last resort for this car.

 

I attended a seminar at Americruise about 20 years ago on cooling. And, the only thing I remember from the seminar was adding a panel under the crossmember like you have to create negative pressure on the engine side of the radiator, and help pull the air through and out. Looking forward to your reported results.

 

I know, louvers are not for everyone. Another thing I did was putting heat wrap on the head pipes from the exhaust manifolds to the mufflers.

 

Rock, experience tells me louvers are more effective then missing panels. The louvers create a reduced pressure area after the louver lip which sucks the air out of the engine compartment.
A missing panel creates a hole that often increases the air turbulence, that does not always equate to removing the air from under the hood.
If you couple the louvers on the lower inner fenders with the air dam you have created, it should make a pretty big difference. Gene

 

In order to louver the upper inner fenders, i would have to disassemble the entire front end. ☹

 

I know I might sound like a smart aleck here (not meaning to), but have you taken off your Hood to see if that allows it to cool and is really the problem? There are some other possibilities-

 

Not yet but I may. I'm convinced this is the problem due to the fact that the carburetor gets heat soaked so easily. I don't have that problem with any of my other cars.

 

That car should have a removable inner panel on the right side to allow access to adjust the valve lash on the original motor. Have you tried just taking that access panel off?

Also, using an electric fuel pump will help big time with any heat related fuel issues you might be having. I was having heat issues with my 52 Dodge when I first got it. I still have the inline six flathead though

 

I was thinking the same thing. Pull the hood and drive it. If it still overheats you have an engine/cooling system issue to address somewhere.
If that works, put it back on and start with removing or louvering the inner fender panels and test driving it again.

How about a small fan in each inner fender panel to pull air out of the engine compartment? Wire them to the thermostat to kick on when your electric fan activates.

In post #28, 48 Plymouth suggested spinning the core support 180 to place the radiator in front of the core and run a mechanical fan. If all the small tricks don't work, you could jury rig the radiator out front temporarily and install a mechanical fan to see if this trial setup works.

Lastly, if the car wasn't paint finished I'd say a possible solution would have been to install a cowl vent of your choice that had a ducted electric exhaust fan built into a screened intake duct at the top of the firewall to suck the hot air from the top of the engine compartment. Puling hot air out should introduce cool fresh air.

 

Just my 2 cents...41/48 fords have a scoop that mounts under the Rad that forces air upward. They also have a shroud that fits over the top of the Rad to help force the oncoming air through the grille. Also, from the pics it looks like your inner shroud is right on the rad...no through air flow to the outer corners?

As said earlier I added an oil cooler and capped off the Rad oil cooler ports and it all seems to help as i too was running hot before adding a shroud and separate oil cooler. Good luck hope you get it takin care off.


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Maybe I missed something on this thread. I haven't seen anywhere that you've actually described what "too hot" means.

Is your radiator burping out so much that it overflows your burp tank? Are you having vapor lock intermittently or while you're driving? Have you researched that fan and found out that those curved blades may not be pumping as much air as a wide paddle fan? Is it getting too hot while going fast or going slow? I'm just thinking we need a little more info about your symptoms before you go cutting on your car.

 

The thing about the wide blade paddle fans is that they can produce more static pressure difference then a thin curved blade but they're a little noisier.

The thing about those fan ratings that are published by the manufacturer is that they ignore the static pressure difference that the fan is able to produce. Literally every fan rating for commercial or industrial applications will give you a quantity of airflow at a certain static pressure and fan rating curves drop significantly with increased static at a given RPM .

A thin bladed fan or one without enough blades can and will actually cavitate and stop giving hardly any air flow at higher static pressure differences. Since you've got a pretty good Radiator on there plus that condenser in front of the radiator you have a high static pressure application with a low static pressure fan.

I just Googled High static pressure fans and this was the first video although he's talking about a different subject and he's kind of a goofy guy, he does explain the differences. you will note that the high static pressure fans have thick wide blades and the low static pressure fans have thinner blades.

Get the right fan in your problems may disappear.

 

This works in 100 degree weather :

https://49fordcoupe.smugmug.com/Under-the-hood-modifications/i-HMC8tfc/A

 

I run a 360 in my 48 Plymouth. I see you have an aluminum radiator. Is it the same size as the original? If so you can mount it in front of the core support (instead of the stock behind the support location) to gain the room for a mechanical fan.

 

If you go to the spal website and peruse 16 inch fans you will see that even they don't even have a rating the 16 inch fan with the thin curved blades like you have other than at zero static pressure. Air flow Goes to Hell in a handbag real quick.

This fan requires a 30 amp circuit, but will pump truck loads more air then what you have... check all the other fans and look at those ratings on the technical information sheet:

https://webstore.spalusa.com/en-us/...s/30102803/va33-ap91-ll-65a-16-p-12v-pk4.aspx

 

I'm in with the no-hood crowd, plus it looks tough.... Give it a try, it would be a good indicator on the trapped air theory.

 

It is in front of the core support. Trust me. I do not have room. I should have recessed the firewall.

 

Thanks. If I had one do over right now, I would have incorporated those flaps and extra holes.

 

So is there a problem with pulling that fan out and replacing it and putting some flap holes and Flaps in your shroud?

And what does "too hot" mean?

 

Remove hood. Place it in the shade.

 

You mentioned earlier about possibly wrapping your ceramic coated headers.I have not seen any manufacturer of ceramic coated headers condone wrapping. Uncoated perhaps-but the ceramic coating in itself will promote lower under hood temps.

 

You need to ensure that airflow is not impeded or allowed to flow anywhere else other than through the radiator so no gaps around it. Once air is trapped there, as already discussed, it just can't escape as it has nowhere to go.
On my 35 Chebby I added reverse louvers to both under fender aprons allowing the air to escape and flow out as they are external and face to the rear. Plus they keep the water out of engine bay. I believe the coated headers help to reduce under hood temperature as well. The louvers enhance the OEM louvers in the hood side curtains to promote good airflow. Plus I use a splash apron to direct air flow through the radiator not allowing it to go under. I also don't use a mechanical fan but an electric pusher fan (cfm) in front of radiator that is hidden by grill. It's thermostatically controlled with on and off settings. In stop start traffic it can get up to 200 degrees but generally stays around 180 degrees or a tad lower depending on the season. The engine needs to run hot and not cold; 'too cold' is as detrimental as 'too hot'. I find coolant works better than plain water.

Another thought, you could also drill a 1/8" hole in thermostat to allow a little more coolant through and reduce air temperature, it has worked for others. Is the radiator handling the heat OK?

A friend built a 'Pommy' rod (Vauxhall) and had huge heat issues even with his 'whiz bank' aluminum radiator, adding vertical louvers to both inner fender aprons allowed the trapped HOT air to finally vent externally under the fenders, finally it ran cooler with a decent air flow. A simple fix and looked OEM; if you didn't know otherwise you'd think the louvers were factory.

A well designed fan shroud will greatly assist a mechanical fan as it guarantees that air is pulled through the complete radiator core and not just the area in front of the fan. I recall reading an article along the lines that the fan blades should only be 1/3 or 2/3 into the shroud to prevent air cavitation as air is drawn through radiator to exit the rear. Air isn't stale and hot which in turn causes heat build up.

 

Another rule of thumb if you add an electric fan:-

• 100cfm for every amp required;
  
• 1,250 CFM for a 4-cylinder;
• 2,000 CFM for a 6-cylinder; and
  
• 2,500 CFM for a 8-cylinder

No amount of CFM will keep an engine cool if the radiator is under-sized or if too much of the grille-opening is obstructed. Run a lower temperature thermostat (175 degrees) and a high amp alternator as high-wattage fan motors require power.

I've heard pros and cons for exhaust wrap.

 

The 16" fan covers most of the radiator area. I will look and see.

Too Hot means when the ambient gets around 80 degrees, the temperature starts to climb above thermostat (185) to about 205. This is with the fan set so that it kicks on at about 195. That means that on a 100 degree day, it could go to 225 or higher. More testing is required as the temps go up in my area but also the fact that it boils fuel and gives me hard start problems with an electric fuel pump is another indicator.

The area around the radiator is all sealed up to the grill, including the bottom. No air gets into the engine compartment without passing through the condensor, radiator and fan shroud. My hope that the engine would stay cool with ram air only at highway speeds may be too much. I may have to set the fan to come on at 185 and run continuously in hot weather. I may have to change fans as was suggested.

I will get to the bottom of this but I will take my time. Thanks for the suggestions. Just so you don't assume that I'm a novice, I am 65 and have been fooling with cars all my life. This fat fender is my first build of this type, however and I'm learning a couple of lessons the hard way but that's ok. I won't forget them going forward.

 

Correct.
You'd need to put some louvres, in the rear of the front outer fenders by the A-posts, to draw air out from inside the wheel wells, as many modern cars now have, although this is about fuel efficiency rather than heat extraction, by aerodynamics are the same.
Louvres in the hood top at the rear edge in front of the windshield would be the best bet though, so low pressure sucks out the heat.

 

Okay so from what I understood you to say just that you believe you're having vapor lock problems? And 220 it's not too high. As you know the boiling point of water is 212 with no radiator cap on. With an 18 PSI radiator cap the radiator will Burp to the tank at about 250 degrees So I'm thinking that you're actual engine operating temperature isn't the problem but vapor lock perhaps is. I had the exact same problem I thought until I discovered that my HEI ignition module would pass out at elevated temperatures and then miraculously wake up as it cooled off. not that I expect that's your problem.

Without taking up a lot of time and room on this thread if you want to see what I did trying to fix my vapor lock problem go here:
https://49fordcoupe.smugmug.com/Fighting-Vapor-Lock/i-SK6fT4k/A

 

Oh hell I forgot something else even though Ford had the forethought to put that baffle above the radiator with a rubber flap gasket that's supposed to come in contact with the hood to keep all the air entering the grill to go through the radiator I found that I had about 1/2 to 3/4 of an inch clearance between that gasket and the hood allowing truck loads of air to bypass the radiator. I'm not familiar with the structure around your radiator but is there any possibility that air is going over your radiator or is it sealed between the radiator and the grill?

I added a baffle between my front grill mount and the top edge of the radiator to stop that situation plus just for the hell of it I put another 10 inch fan as a pusher. I had to move my horns and cut-out the back side of the grill to make it all fit but it finally did.

 

Obviously, I don't need louvers, but do like the looks....I can see they might help your Mayflower.

The ceramic-coated headers, for the flathead in my Jeep, might have been cooler than Chrome, or painted ones, but they still were huge heat generators. As you can see everything's out in the open, but I do have fenders on it, now.

Eevery time I was at a traffic light, I could feel a blast of heat from the headers and exhaust pipes. So, I decided to wrap the headers and pipes all the way back to the mufflers. I can assure you that I could feel a big difference, immediately!

I just leave my electric fan on all the time....temp's about 185-190, running hard, or not.

 

It is sealed. I'm thinking about removing the cowl lacing and replacing it with a few bumpers. That would leave a small air gap at the rear of the hood and could help just a little.

 

I like your thinking here how about a rubber intermittent self adhesive cowl lacing.i had an overheating issue where my 16 spal fan was coming on while cruising on a not so hot day.i concluded that my fan shroud was restricting air flow.the hottest water in the rad is at the top so I started drilling there,eventually drilled it top to bottom as I had it out.meant to put some flaps at the top but havnt got around to it yet.shroud is a pita to remove.a two man job to remove and replace without scratching everything.anyway drilling the holes stopped the overheating problem fan hasn't cut in since and the weather has been warmer lately.shroud looks similar to yours.those 16"spal fans shift some amount of hot air when they cut in ,I recommend them but mount it up as high as you can on the shroud for best results.
ps.my hood sides have long original louvres,inner wings have too and there is plenty room for air to exit under the cab. 38 chevy 1/2 ton pu