KoolKote is an aerospace quality hard anodize applied to all surfaces of the piston with a
Exhaust Manifolds - Whether cast iron or tubing headers, there are multiple benefits from properly coating these parts. Aside from appearance, corrosion resistance and surface temperature in proximity to the manifolds/headers, there can be improved exhaust flow and engine performance. Coatings companies often have specific recommendations to make, pertaining to power increases, so you may want to consult with your coatings provider for their take on the subject.
Over time, as the number and type of coatings materials have evolved into their current status, so have the ways to apply them. In many instances, specialized equipment and curing techniques are required, as determined by the material and its application process. However, at the same time, materials have become available that can be applied by the engine builder/racer.
Coatings for cylinder walls, headers, camshafts, valve springs, and pistons (crowns and skirts) are currently available and require only a modicum of equipment and skill level. There's even material suitable for coating racecar floor panels to reduce heat radiating from the exhaust system, if headers are in close proximity to this area. Your best bet is to consult with the coatings manufacturer of choice about material type and application methods.
As previously mentioned, and based on his life-long career building and evaluating a wide range of racing engines, we posed a half-dozen or so pertinent questions to Dennis Wells of Wells Racing Engines.
Q: What was the deciding factor in your decision to try coated parts?
Wells: We'd been seeing some abnormally high oil temperature in one of our Silver Crown cars and figured it would be worth trying. Actually, we couldn't keep the oil temperature down below 300 degrees, and even though I'd heard some coatings could increase horsepower, we were mainly interested in reducing heat transfer into the oil. So we decided to coat the piston crowns and skirts. We figured this would keep more heat in the combustion space and allow less to migrate into the oil. Although I'm not certain what this particular effort did for power, we saw significant reductions in oil temperature.
Q: In your experience thus far with coatings, have you applied the materials yourself or enlisted the services of a coatings company?
Wells: Actually, we decided to try it ourselves. As it turned out, we spent more time doing the preparation steps than the actual coating. The coating and baking in an oven were the easy parts. But I can tell you it was worth the effort. We'd been replacing pistons far more frequently than we should have until we tried the coating. I think later this year we may try to use the services of a coatings company who I'm told have newer materials that they apply themselves.
Q: Have you explored coating other areas of engines and what results have you noted?
Wells: In that same Silver Crown motor we coated the oil pan, crankshaft, rods and valves. In fact, at one point, we rebuilt the engine and didn't have time to coat the pistons. The driver immediately reported the oil temperature was about forty degrees higher. So we tore it down, coated the pistons again and the temperature went right back down to where it'd been when we coated them the first time.
We've also experimented with coating valve springs, but because some of the spring material we're now using, and the fact most of our races are short compared to a Cup track and distance, I'm not sure how much the coating would help. But we did see some benefits early before the springs we're now using. I expect in longer races, especially with multiple spring assemblies, you'd see more benefit that what we've observed in our racing conditions.
Q: Based on friction horsepower reductions and heat retention in the combustion space, have you been able to measure any power gains?
Wells: You know, we've never really tried to nail this down. The fact that coating the pistons had such a beneficial effect on our problem with oil temperature, I've not been too concerned about the effects on horsepower. However, I will say that it would appear we've seen gains around 5-10hp, but I want to emphasize that wasn't our primary goal. Had it been, we might have spent more time trying to figure out how to maximize the possibility. I guess I'm basing this on the ASCS engines we've done with and without coated pistons. These are where we've measured the gains.