The valve cover cover is a heat blanket developed by Advanced Thermal Products in Irvine, CA. It is custom fitted to the valve cover. I also so have the exhaust manifold, turbo charger (exhaust side), exhaust down pipe, and oil pan covered with the same material. This heat blanket is designed to easily withstand temperatures well above 2,000 degrees F., so the material does not deteriorate.
The engine compartment runs considerably cooler, the seals in the exhaust brake vacuum cylinder don't get scorched, and the passenger side floor now stays cool when pulling a long grade on a hot day. My wife likes that.
There are noise reduction benefits, as well. The raucous idle clatter is subdued when standing outside of the vehicle as well as when sitting inside or driving down the road with the windows up or down. My wife likes that, too.
The purpose for covering the valve cover and oil pan was for engine noise reduction only. The purpose for covering the exhaust components was for heat reduction in the engine compartment. There was some noise reduction benefit, as well.
- John