Radiator Air Flow

William Kelchner

William Kelchner

Senior Member
Years ago when I bought my car it would overheat. Eventually found out that needed timing. Since then replaced the radiator, water pump. Car no longer overheats and quit back when I discovered the timing was way off.

I moved my license plate to the bumper thinking maybe I would get a few more inches of cooling to the radiator - just never got around to moving the plate back to the headlight bar - another item on the list.

Just curious did it really matter back then or were the bean counters at Ford just saving a few cents by drilling the headlight bar vice fabricating a bumper mount.
 

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Headlight bars were only drilled for a short time in 1930, and all the rest used license clips to hold the plate to the bar. The is very little cooling difference by not having the plate on the bar.
 
Just measure the plate, and the total surface of the exposed radiator. That is approximately the amount of air flow you will lose. Add the surface of the radiator badges, and the cross sectional area of the wires on a stone guard, then see what is left. there will be a small amount of air wrap around these objects but not much.
I am sure there will be some that do not agree but these comments are based on 40 years experience in Industrial air systems design.

I do mount my plate on the bar in cool weather, but in warm weather it moves to the bumper. I have no issues with overheating or vapor lock, and do trips in 100 degree plus weather.
 
Plate or no plate on the headlamp bar you still have coolant flowing through the tubes and air being pulled through the fins by the fan, so the area behind the plate is NOT cut out of the cooling.
 
That might be partially true when not moving, but when moving, the plate acts as a block and not only limits moving air to the area behind the plate, it creates a wave across the surface of the radiator. Wind tunnel testing has proven this. The amount of air actually pulled by the fan is mostly the cross section of air that is directly in front of the fan, bordered by its circumference of travel. This is exactly why more modern cars went to fan shrouds. When a plate is placed in front of the radiator, it increases the static pressure directly behind the plate, and if there was a shroud it would just increase the air flow at the outer edges. But since there is no shroud it tends to draw more air from the sides of the fan blades behind the radiator as the static pressure is lower there. The air flow is not cut out by a plate, but is drastically reduced especially when cruising.
 
My 29 had a 4 blade fan and engine pans. Even at idle, you could put your hand in front of the radiator and actually feel the suction of the air flow through the radiator.
 
whirnot said:
.... When a plate is placed in front of the radiator, it increases the static pressure directly behind the plate, and if there was a shroud it would just increase the air flow at the outer edges. But since there is no shroud it tends to draw more air from the sides of the fan blades behind the radiator as the static pressure is lower there.....
Click to expand...

Bill,
I'm not questioning your conclusions, but I'm struggling to follow the rationale, specifically, why would flow from a high pressure area be impeded? My understanding is that air flows spontaneously from higher to lower pressure areas.
Steve
 
Humble opinion, FWIW:

1. Overheating?

2. Causes of overheating often mentioned & suspected causes often tried to correct may include incorrect ignition timing, brakes dragging, wheel bearings too tight, parts of engine too tight, carburetor too lean, stale gas, radiator stone guard blocking air flow, etc.

3. Even though the above items can add to overheating problems, appears the real root of the problem in 99% of the cases is avoided most of the times because of the cost involved to correct, or time involved to correct; i.e., thoroughly cleaning the interior of the radiator; e.g., making sure that the flow of coolant is not being reduced inside the radiator caused by interior tubes being partially blocked with scale, grease, rust, dirt, etc., not necessarily in that order; or increasing interior coolant flow by re-coring the radiator.

4. Less expensive & less time consuming quick fixes may include tightening a slipping fan belt which reduces air flow & causing less water to be circulated through the water pump, and/or replacing a defective thermostat.

5. If we have 80+ year old radiators in any type & make of engine's cooling system, after thoroughly checking (2.) & (4.) above, we often find that item (3.) above was the basic cause of engine overheating & that in most cases, (2) & (4) above just added to the item (3.) problem.

6. Appears female drivers would always choose (3.) first -- they think differently. LOL
 
Percentage wise the plate blocks quite a bit of radiator surface. On our cross country trips if the weather was really hot I would raise the plate to the horizontal position. Never had a problem.
 
steve s said:
Bill,
I'm not questioning your conclusions, but I'm struggling to follow the rationale, specifically, why would flow from a high pressure area be impeded? My understanding is that air flows spontaneously from higher to lower pressure areas.
Steve
Click to expand...

You are correct I should have said it DECREASES static pressure. and velocity.
 
Thanks Bill & Bill for the bumper bracket tips. Got my 1931 plate restored. This one is going on the front and I like a bumper mount. :)
 

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Nice SkipShift. To state the obvious ensure the plate is not in line with the front tire and any debris that may be thrown into the back of your lovely plate.:o
 
Or you can make a bracket similar to a rear bracket and mount it to the bumper using the center clamp. It can be above or below the bumper.
I did that using a piece of stainless Steel.
 

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I remember my grandfather telling me that they used to just loosen the clamp bolts a touch then when the weather turned hot you could just grab the bottom of the plate and pull it up so that it stuck straight out flat , then when it got cooler you just push it back down, simple enough
 
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