#2 the coating is a thermal barrier, thus keeping heat within the manifold or header. There are a number of benefits for this. First, by keeping heat within the manifold, you're going to accelerate the exhaust gas velocity which reduces back pressure and reduces fuel contamination due to reversion. This is a performance benefit. Second, you'll reduce the surface temperature of the manifold. This means if a person comes in contact with it, they are less likely to be burned and leave skin behind. If there is a component close to it, it will not see as much heat as it would with an uncoated manifold. In addition, not as much heat will be radiated under the hood or into the engine compartment. This reduces the underwood temperature which, again, reduces the temperature of surrounding parts, such as, alternators and starters. It also reduces the amount of heat that can be drawn in through the carburetor, which is a secondary performance benefit. There are a variety of coatings that can be used on exhaust manifolds or headers.
Color Schemes can play a large part in custom cars. For tube steel headers, the engine application may need added protection. 9 to 1 Comp. Engines naturally have a hotter exhaust.Chrome headers have a problem with turning brown, blue and purple. Note: (Thermal barriers are intended to reduce heat transfer by about 30% on the average. Chrome will start turning brown around 450 degrees, turn blue around 500 degrees and after that they just look nasty. Chrome looks good but is not durable.