that the heat wrap will make your headers rust out prematurely...I have the ceramic coated headers on my 53 Chevy but bought them coated to help preserve the headers...not to cut down on under hood heat???
I would have said ceramic all the way before I talked to a ceramic coating place and I am not that sold on the ceramic now. I was always under the impression that the ceramic was inside and out and would not cause the headers to see higher than normal heat by trapping heat in the metal like the wrap. After talking to a ceramic place, I was told that all of the coatings are a spray on and bake type and it is impossible to coat on the inside. The guy said untill someone comes up with a dip type process everything will be inside only and as far as they can spray on the inside.
What you were told is true. The Ceramic coatings are sprayed on. They can only get so far inside. However that is not a problem.
The problem with header wraps is thay they trap moisture and heat. The rust will start between the wrap and the header. The wrap will destroy a set of cheap headers in very short order.
With coatings there is no way for moisture to get between the coating and the header, so there is no rust issue. There is not much moisture sitting inside a header, what little does form is quicky burned off when the engine is started.
If you want to see what header wrap will do, just put a wet blanket on a piece of plain sheet metal let it sit there for a few months and see what you have. It's the same effect as trapped leaves in the lower fender area, that's where you always see certain cars with rot. The reason is the trapped moisture.