Inner fender louvers

oldford2

oldford2

Well-known member
Many cars in the 20's, 30's had louvers on the inner fenders. I would think it would be good on the 40's also. It has been upper 80's here in the Northeast for 2 weeks and no end in sight. We use our 46 3 or 4 times a week for our errands and short cruises. No overheating or hard starts when warm. When we stop at the supermarket I lift the hood a foot or so to let the heat from the engine escape. Then to restart it I push the pedal to the floor and hold it. Starts first or second turn always.
We have "factory air" on the 46 (cowl scoop and wide open vent windows:)) But doesn't work too good at stop lights
So, I think inner fender louvers would help but too late now.
John
 
My experiences (and some semi-scientific testing) suggest that inner fender louvers may actually be a detriment to cooling.

Given that the radiator is properly matched to the motor and the coolant movement works properly the only factor left is air flow through the radiator. At slow speeds the fan moves air through the radiator. At some speed the fan becomes a minor player as the air is moved by a difference in frontal pressure (through the grille) and the air behind the radiator in the motor compartment.

The issue is that fenders act as an air scoop, causing a high pressure area behind and on top of the wheel. Inner fender louvers might help with air release from the motor compartment when the car is stopped but at speed the excess pressure will move into the motor compartment and lessen or even stop air flow through the radiator. Fords through 1939 (except 39 Deluxe) had hood side louvers which allowed air flow that is not affected by the fenders.

The 1939 Deluxe and 1940 Ford had a air dump at the back of the inner fender, and VERY IMPORTANT, a baffle type fender brace. This brace has a high air flow under it which causes a "venturi" effect to release pressure at the back of the fender where the air dump is. The problem is that it is only effective to about 50 mph or so. Above that the air will flow at pressure above it and inhibit cooling. The work arounds are to remove the motor pans and block the air dump, or to extend the baffle brace to the top of the fender.

Many of the under grille pans from 1937 on have lips that point down. These will also provide a "venturi" effect to help scavenge air from the motor compartment. Many street rod types (and restorer types too) do not realize the importance to cooling these panels have and forget to install them.

A good proof of this is that modern cars do not have louvers between the fender compartment and the motor compartment. If it were to help cooling the engineers in Dearborn, Yokohama, and Berlin would be using them now.
 
Karl, I found what you said to be very interesting.
"Above that the air will flow at pressure above it and inhibit cooling. The work arounds are to remove the motor pans and block the air dump, or to extend the baffle brace to the top of the fender." I would be interested to hear more specific info. about the "work arounds". On my 40 I have removed both engine pans but still have the stock fender splash pans installed behind the front wheels. What can be done to these to improve hot air flow out of the engine compartment? Not sure what you mean by "extend baffle brace." Photos are of underneath the left front fender.
 

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There is several inches of space above the baffle brace... extending that up to about 1/4" from the fender is what is needed... The idea is to not allow air from around the tire to pass over the top of the baffle. When the air passes below the baffle it is at a relatively high velocity and the venturi effect occurs. Bitchin Products used to make extended baffle braces but they are out of business and no one else has picked them up.
 
Karl, Here's a sketch showing the OEM inner fender splash pan and the extension at the top which would follow the contour of the top of the inner fender and be about 1/4 inch away from the top of the inner fender. The leading edge of the extension would be even with the centerline of the tire or maybe an inch or two behind it. Is this the corrrect representation of your idea? I am thinking of getting another set of inner fender panels and trying your extension idea. Would it be a good idea to make the leading edge of the extension the same shape as an airplane wing or just leave it as a flat piece of sheet metal? Thanks. JIM
 

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The 41s have the "air dump" at the rear of the inner fender as well so I guess they continued that trend into the 40s. I assumed the 42s thru 48s had them as well but I don't know for sure.
 
I understand 40's are some of the hardest to cool. Since I am not 100 percent stock this winter I was planing one row of louvers just under the belt line of the hood. I think this should help drawing heat out of the engine bay.
 
Jon: Not sure where "one row of louvers just under the belt line of the hood." would be but I doubt if one row of louvres will make any difference. PLUS few things look worse than louvres in a 40 Ford hood. It ruins the smooth flow of the hood. If you must have louvres get the louvered inner fender panels. Try other ideas first, like blocking air flow to top of hood and in top/front of radiator grill brace. Shroud helps too. Whatever you do, please don't louvre your hood. Once done, you can't go back to those beautiful Bob Gregorie lines.
 

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Of course my 40 is a pickup so I have a little more room between the top of the fenders and the hood molding (embossment) running the length of the hood. Maybe your right about the escaping under hood heat. I have already blocked airflow to the top of the hood, and have a shrouded electric fan pulling air. It would be nice if I didn't see creeping temps, but I didn't know some felt so strongly about the hood lines :)
 
Gee, I think I saw these for sale in an old JC Whitney catalog, "Guaranteed to reduce engine temperature by 20° AND reduces aerodynamic drag with a 30% improvement in gas mileage!"

:-)
 
oldford2 said:
Many cars in the 20's, 30's had louvers on the inner fenders. I would think it would be good on the 40's also. It has been upper 80's here in the Northeast for 2 weeks and no end in sight. We use our 46 3 or 4 times a week for our errands and short cruises. No overheating or hard starts when warm. When we stop at the supermarket I lift the hood a foot or so to let the heat from the engine escape. Then to restart it I push the pedal to the floor and hold it. Starts first or second turn always.
We have "factory air" on the 46 (cowl scoop and wide open vent windows:)) But doesn't work too good at stop lights
So, I think inner fender louvers would help but too late now.
John
Click to expand...
Perhaps more engineering went into the design than most folks realize or would have thought.

I had seen a factory film with a '40 in a "wind tunnel" showing the effect of the circulation beneath the hood both with the engine pans and without. The difference was remarkable.
Those pans, often missing, are paramount in aiding proper heat dissipation beneath the hood.
That may be the reason those pans are listed in the parts book in the radiator / cooling section.
 
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