It has been the topic of Dirt Tech numerous times: Dirt track racing is often as much about protecting your car from the elements to ensure that it will finish the race as it is about outright speed.
One area that can be particularly vulnerable is the radiator. Perched at the very front of the car, the radiator is susceptible to rocks, dirt clods, and racecar debris that can be thrown up and puncture the core. Although they may not be able to knock a radiator out with one hit, smaller chunks of junk can also do damage by bending the cooling fins, reducing the radiator's efficiency, and causing the engine to run hotter. And finally, mud and small grains of dirt can clog the radiator, keeping air from flowing through and drastically reducing its ability to keep the engine cool.
To protect the radiator, racers often cut only a minimum number of cooling holes in the front nosepiece-or none at all. Also, to keep from trapping a lot of dirt and mud, dirt cars rarely have a full radiator box or ductwork driving air to the radiator. Instead, you can usually get enough air with only the two sides while leaving the bottom open. And finally, to keep a buildup of dirt and mud from choking off the front of the radiator, you can install or fabricate a "shaker screen." The shaker screen is designed to catch dirt, mud, and other debris before it reaches the front of the radiator. It is mounted loosely in the car so that it either swings or rattles as the car travels around the track. This movement shakes the mud loose so that it falls back to the track and leaves the radiator unclogged.
Together, these measures can help protect your radiator so that you can concentrate on driving and not worry about spilling coolant all over the dirt. We recently stopped by the race shop of Robbie "Frog" Jordan as he neared completion of his MastersBilt-chassied car and watched as he fabricated a radiator box and installed a shaker screen. This is by no means the only way to do it, but this should give you some ideas on building your own radiator box and shaker screen.
Mud and clay are fun to race on, but they can also be the enemy to the mechanical components of your racecar. This is obviously an extreme example, but protecting your radiator from the elements while also promoting good airflow for plenty of cooling is critical to your success on the racetrack. | 
Most dirt racers find that they can get enough air to the radiator without having to cut holes in the front bumper cover, as you can see here in Robbie Jordan's current car. This helps protect the vulnerable radiator from flying debris. | 
Before beginning fabrication of any radiator ductwork, Jordan installs the radiator and all related components as well as the nosepiece. This gives him his dimensions for the sheetmetal. The bottom of the radiator box will be left open to allow plenty of air to the radiator, and two sides will be fabricated to make sure that the air coming underneath the car will be forced though the radiator core instead of around it. The hood will form the top of the duct. |
Jordan begins by making cardboard templates of the pieces he eventually will fabricate from aluminum sheet. Cut small pieces and slowly trim the cardboard down until you get exactly what you want. If you mess up, you can always tape a chunk of cardboard back onto your template and start over. | 
Don't forget to plan how you will mount your sides to the car. It needs to be easily and quickly removed if you need to repair wreck damage at the track. Here, Jordan marks a hole that will need to be cut in his template with a drill bit. | 
Once the template meets his approval, Jordan traces the shape on a sheet of aluminum and cuts it out. Save the cardboard template in case the original gets damaged beyond repair and you need to fabricate a new radiator box. |