"General, we can rebuild him. We have the technology."
If you can remember that famous line, then you probably watched a lot of episodes from the television show The Six Million Dollar Man. Of course, that show went off the air more than 30 years ago, so if you're old enough to remember it you may not want to admit it.
In case you don't know that show, it was all about how the government created the first bionic human being and used him as a weapon to fight crime. We don't have anything to do with that here at Circle Track, but we are all about using technology to make our lives better when it comes to racing.
High-tech coating processes are one area that is definitely allowing us to make existing parts better. Of course, this is nothing really new. Forward-thinking engine builders and racing teams have been using coatings on everything from headers, to pistons, to floor panels for a while now. The question is, are you?
Engine Internals
Coatings first caught on in racing with exhaust headers, and that's where the technology is still the most popular. We will get into headers in a moment, but first it's important to remember that properly selected and applied coatings can be beneficial in other areas too.
Because Jet-Hot’s header coating...
Because Jet-Hot’s header coating is only around 0.0025-inch thick, it can coat the flange to protect it as well without affecting the gasket’s ability to seal between the exhaust ports in the head and the flange.
Dave Burton is an engineer with Jet-Hot High Performance Coatings and says that coatings are useful in the engine for reducing friction and directing heat where you want it. "We've had success putting a thermal barrier on the top of a piston," he says. "The coating that we use is a ceramic metallic coating that is excellent at resisting the heat of combustion. "It works because it has a reflective property. It actually reflects heat from combustion back into the combustion chamber itself. The coating also helps keep the heat more uniform throughout all the surfaces in the chamber. This helps eliminate hot spots. Now when the air/fuel mixture hits a surface in the chamber, including the piston top, it atomizes better and that is giving you a good, uniform fuel charge to burn and make power with."
In addition, coating the piston skirts--the sides that rub against the cylinder walls--with a friction-fighting coating can improve both power and engine longevity. Different operations use coatings that may work differently. Jet-Hot, for example, uses an antifriction coating, called Slick Coat, that promotes lubricity on its own. Other antifriction coatings work by creating a surface that oil clings to, and the oil provides the lubricity.
Either way, an antifriction coating on the piston skirts can help prevent damage on cold starts after the oil has drained away from the cylinder walls and in the event your engine experiences a drop in oil pressure. The result is the coating not only protects the pistons, but also the crosshatch honing in the cylinder walls. This is important because keeping the crosshatch in good condition improves oil control and helps minimize blow-by. Plus, the antifriction coating can also help cut down on drag inside the engine, freeing up more power to be sent to the rear wheels.
"The valves also work a lot like the pistons," Burton adds. "You can achieve the same thing with a thermal barrier coating on the end of the valve and a friction fighter on the stems. That helps reflect heat into the chamber and the antifriction coating can help reduce the chances of a valve sticking in the guide.
Coatings aren’t only for headers....
Coatings aren’t only for headers. These pistons have received a heat reflective coating to help keep the heat from ignition in the chamber for better flame travel. The skirts have also been given an antifriction coating to help prevent scuffing both the piston skirts and the cylinder walls in the event of a drop in oil pressure.
"Valvesprings are also something that we ran across in testing that can be improved with a coating," he continues. "We did a test where we installed coated valvesprings on one bank of a Sprint Car engine and uncoated springs on the opposite bank. Then we went and raced the car. Afterward, we pulled the valvesprings and tested them. The coated valvesprings showed less loss of tension on the springs. That's neat because in circle track racing everybody is really trying to push the rpms, and that's really stressing the valvesprings. That coating was our Slick Coat product, and I think it helped because it allowed the oil to hit the spring and then move off and not cling to it. It pulled the heat away from the springs and that helped them live longer and work more dependably."
Application
Some coatings manufacturers have developed mixtures that can be applied by just about anybody in their own shop. And some of these work rather well, but Burton says Jet-Hot believes that every bit as important as the coating formula is how precisely it is applied, so the company handles all applications itself.
Of course, the application process for Jet-Hot's high temp coatings probably isn't something you would want to try for yourself anyway. "Our higher temperature coatings are what are called 'combustion sprayed coatings,'" Burton explains. "Those are metallic and ceramic blends or on the extreme high-temperature coatings, they are all ceramic. To apply the coating, it goes down through an oxyacetylene torch that heats up the particles so that they are actually melted while they are in the air before they strike the component to be coated. They then spread out and make a bond with the part itself. As you can imagine, it takes some very specialized equipment to achieve a proper bond with a combustion-sprayed coating, but for what it does, this type of coating is unmatched."
Header Tech
Although there are lots of different areas where coatings are beneficial, headers are still the most popular component to be coated. Most Saturday night racers use less expensive, mild steel headers versus stainless, but mild steel is subject to corrosion--both thermal and chemical. Application of the proper coating can not only protect the metal to increase its useful lifespan, but it also helps improve performance.
A heat-reflective coating helps keep exhaust heat inside the header tubes until it exits the exhaust system. This keeps the heat from radiating into the engine compartment which, in turn, lowers the temperature of the air entering the carburetor. Burton says the heat retained in the exhaust headers also lowers the overall pressure inside the exhaust system. This helps evacuate the burnt gasses from the higher pressure combustion chamber into the lower pressure exhaust ports and headers more efficiently.
Of course, header wraps do the same thing, and they are generally cheaper. But while a wrap can provide the same insulating properties as a coating, it can't provide the same protection from corrosion.
If you race a Pure Stock class...
If you race a Pure Stock class that requires running the stock cast-iron exhaust logs, insulating coatings also work here, too. They can help keep the air inside the engine compartment cooler, which is important since that is the air that’s getting sucked into the carburetor.
"From only a thermal standpoint, wraps do pretty good," Burton explains. "They are thicker than a coating, and any time you have more thickness it is easier to insulate against heat. But what a wrap doesn't do is provide any protection from the air and moisture that can still work its way down to the metal. You have not sealed the surface from water or air, and extreme heat cycling combined with the presence of air and water is what really damages exhaust parts. That's what causes the process of thermal oxidation. A coating, because it completely covers the metal, seals it off from both air and moisture and can provide the protection from rust and corrosion that a wrap can't.
Because Jet-Hot’s header coating...
Because Jet-Hot’s header coating is only around 0.0025-inch thick, it can coat the flange to protect it as well without affecting the gasket’s ability to seal between the exhaust ports in the head and the flange.
Coatings aren’t only for headers....
Coatings aren’t only for headers. These pistons have received a heat reflective coating to help keep the heat from ignition in the chamber for better flame travel. The skirts have also been given an antifriction coating to help prevent scuffing both the piston skirts and the cylinder walls in the event of a drop in oil pressure.
If you race a Pure Stock class...
If you race a Pure Stock class that requires running the stock cast-iron exhaust logs, insulating coatings also work here, too. They can help keep the air inside the engine compartment cooler, which is important since that is the air that’s getting sucked into the carburetor.