In competition on dirt, more so than in any other form of motorsports, the battle is not just against other drivers. Dirt racers also have to battle the track by keeping it out of the various mechanical systems on the car. Dirt can ruin a very expensive engine, transmission, rearend, brakes, and the cooling system. And dirt seems to find its way into the various systems of the car no matter how hard you try to keep it out.
The EngineThe most recognizable and fundamental dirt blocker is the engine air filter. The intent is to supply the engine with a constant stream of clean air. Nothing will ruin your day at the races quicker than getting a stone or large clump of dirt past the carburetor and having it go through the engine. The damage does not have to be instant to be detrimental.
A poorly maintained filter, or one that is ill suited to the task at hand, can do just as much damage as not running a filter at all. Drawing in a constant stream of dusty air can destroy the rings, cylinders, and valves. This same dirt can then get passed to the oil and the damage just keeps accelerating. This kind of damage can be progressive or sudden. Passing a small stone into the engine will do some serious damage, ending your day at the races and providing a weight loss scenario for your wallet. But a filter that continually allows dirt to pass is just as damaging as a stone or any other hard object that might go through the engine. It is just that the damage will be seen in a much shorter useful life as opposed to an instant catastrophic failure.
Most circle track engines will also have at least one crankcase breather installed in the valve covers. They may even have two. The pressure changes internal to the engine on the bottom side of the pistons can be volatile. The act of the pistons traveling up and down at high speed can, and does, create some rather large swings in the crankcase pressure. Engines that are fitted with a dry sump pump can actually develop a vacuum in the crankcase. This can make the sealing of the engine crankcase a difficult proposition. For the majority of the Saturday night racers who are not running a dry sump oil system the standard solution is to vent the crankcase to ambient air. This has to be done carefully. It is just as easy to draw dirt or foreign objects through a breather as you can through the air cleaner and the potential for damage is just as great. The breather should be routed through a filter that will prevent any dirt or other objects from entering the engine.
Many of the engines used in classes run by the Saturday night racers have a breather system that was designed by the OEM (Original Equipment Manufacturer). The volume of air these systems were designed to handle is not sufficient for the higher rpm application that will be seen by the racer. I am speaking of engines in the Street Stock classes and even some of the more advanced classes. As the rpm increases and is sustained, the stock breather systems will not be able to cope with the amount of air that will be moving through the breather. This elevated rpm results in pressure building in the crankcase and that can cause oil leaks and a path for dirt to enter the engine.
The simple fix is to remove the stock breathers if your local rules allow this and replace the stock breather(s) with a system more suitable for a racing application. There are many systems available that will bolt to your engine and solve this problem without too much cost or real effort to install. It is an easy fix to a potentially damaging problem.
Many of the Saturday night racers use automatic transmissions and the simple fact is that these are, and should be, a sealed unit. If they are leaking you need to locate the source of the leak and fix it. If you are running a manual transmission you can generate some serious pressures in the gearbox and should consider a vent. If the gearbox has a pump that routes gear oil to a cooler, you still should consider a vent that utilizes a filter to keep dirt or other debris from entering the transmission.
The reason that we need vents in the transmission is that the rpm levels the engines are running are substantially higher than the transmissions were designed to see in the original applications. Even gearboxes that were designed for racing should be vented to prevent built-up pressure in the box. The gears spinning in the oil produce a good bit of windage and that can cause pressures to build much the same way that the engine can produce pressures in the crankcase, and this can cause oil leakage at gaskets and seal interfaces. Not a good thing. The same logic that applies to the engine breathers also applies to gearboxes. The vent should be routed through a filter and the vent needs to be located above the oil level.
The concern here is not so much contamination but physical intrusions into the brakes and specifically between the brake, wheel, and disc interfaces. Such intrusions can be avoided by building a small shield that will prevent anything from entering or getting trapped between the brake and the wheel or from entering the caliper. There are also some shields on the market that fit between the wheel and the brake that help prevent anything hard from going through the wheel into the brake. These shields also help to minimize brake dust from getting on the wheel.
If you run in a class where pit stops can be an issue, you want to avoid the possibility that a lug nut could get caught between the wheel and any part of the caliper or disc. If a lug wedges itself between the wheel and the hub after a pit stop, the lug could cause a wheel to loosen or damage the wheel and the brake, ending your day at the track on a sour note. Brackets to prevent this are easy to make and some are available from brake vendors.
Keeping dirt out of your fuel system is not as easy as you would think. The best way to keep the fuel system clean is to not allow anything but fuel into the system in the first place. (Thank you, Captain Obvious.) While this is easy to say, it is a bit more difficult to accomplish. The first place to start is with fuel transfer equipment. Keep your fuel cans clean inside and out. Make sure that the area around the fuel inlet is clean prior to even opening the fuel cap. This is an easy thing to let slip if you are racing a dirt car. Mud is usually everywhere, so take the time to clean the area around the fuel filler prior to even opening the cap.
It doesn't hurt to run a filter in the funnel so any dirt can be caught prior to entering the fuel system. If you are running a stock fuel tank on your Street Stock or Bomber class racer, take the time to remove the tank and clean it thoroughly. If not, the loads and the shocks that you will be placing on the tank will break loose any rust and scale that will have formed in the previous 15 to 20 years the car was used as a passenger car. The amount of rust scale and general debris that can accumulate in a fuel tank over time is significant.
Even after you take the time to clean the tank and keep the fuel entering the tank clean, you still need to run a quality high-volume filter. You will be using more fuel in a racing application than the previous street application so you need to up the capacity of the fuel filtering system on the car. There are many quality fuel system components on the market that will help you to achieve a trouble-free fuel system for your racer. Do the research, plan, and execute to make sure you are using sufficient filter size to supply the engine with clean fuel.
We are not as concerned with dirt in the cooling system as we are with covering the radiator with mud and blocking the flow of air and creating a situation where the radiator cannot do its job. Dirt on the radiator can cause overheating and we need to be concerned with potential damage to the radiator by an errant flying rock or dirt clod. It is not uncommon for the radiator to become damaged and start leaking. Aside from the potential damage to the engine from overheating, this damage can be an expensive repair, coming close to several hundred dollars. In a class where you are racing for smaller purses, it especially makes sense to avoid that type of expense. The solution to external damage may be as simple as placing a heavy metal screen on the front of the car to block foreign matter from impacting the radiator.
Keeping the various systems of the car clean is all about planning and execution. Look at what could happen and take the actions to prevent it from happening to you and your racecar. This is something that does not require any innovative thinking in an attempt to create something new and special. It is a case where the racers who have come before you have developed some very effective methods to keep the dirt out. It is up to you to take the effort to install similar devices on your car. Make sure the lessons of the past are incorporated into your car. You can use the time you save not thinking about how to solve problems that are already solved and use that time to work on the problems that are yet to be solved. It's just that simple.
The author can be reached at Vahok.Hill@cox.net