I started testing this closed grill on my '88 Dodge Ram 150 powered by a 318 cubic inch TBI engine
But all that time was without a front bumper which might effect the airflow from down low.
As I've finally settled on a design for my bumper that will be lower to the ground than the original bumper, I thought today would ne a good time to build an air dam that will help channel air flow through a vent I'm planning on putting in the middle of the new bumper, and redirect that air to the radiator, air conditioning condenser, and the huge aftermarket transmission cooler I installed some years back to keep the 767 Torque flite Automatic Transmission cool.
I began by cutting a piece of steel angle to length and bolting it across the frame rails after painting it with Rust-Oleum rust resistant paint. Then I found some pieces of scrap gray 1/16" ABS plastic sheet and started drilling and bolting them to the angle with lots of 1/4 - 20 bolts, nuts, and washers.
In the corners, I heated pieces of the ABS with my heat gun and bent them against a piece of angle iron clamped in my bench vice. I could have made better corners had I used the bending break in the shop, but as the shop is over 30 minutes away I decided I could make do.
The hoses for the transmission cooler pass through the top of the air dam just off center. I made sure to protect them from chaffing.
I have the ability to add a flexible rubber extension to the bottom of the air dam in the future should I need more airflow and I can even adjust the angle on my current arrangement if I need to, but until I build the bumper I'm just going to see how it works.
Since the 1970s most modern cars have come from the factory with air dams or as they are often called, spoilers. Most people think they are for aerodynamics, performance, or looks, but while they are added to cars for those reasons, the primary reason most cars have air dams is to prevent overheating.
Years ago, while working in a radiator shop, people would often come in complaining their Trans-Ams and Camaros were overheating despite having replaced everything that commonly caused overheating. Other cars had the same problems but those were the most common. The 2 most common causes were not having fan shrouds and/or air dams. Of course, every customer I explained that to thought me crazy or trying to rip them off, but the few who listened were pleasantly surprised.
Fan shrouds have been on pick-ups for a very long time but now days even pick-ups are coming from the factory with air dams as manufacturers look to reduce grill openings as a means to increase aerodynamics and fuel mileage.
This thing is forcing so much air through the radiator I'm going to have to design and install an automatic mechanism to open and close it based on engine temperature as the engine runs cooler the faster I drive. Or, drive slow.
Next I start building the bumper bar and fiberglass bumper cover with an opening in the center of the bumper to allow for air flow to the engine and cooling system.
After the bumper is finished I will continue the air dam around each side of the bumper along the bottom to route air around the truck instead of under the truck. Then it's on to aerodynamic underbody side skirts and a rear bumper to complete the package before everything comes back off for sanding and final painting.